A Conservative former minister has "outed" himself as a poppers user, amid warnings that a Government ban on the substance will harm the gay community and others.
Crispin Blunt warned he and many gay men are "astonished" by the Government's proposals, adding respect for the law would "fly out the window" if a ban is implemented.
He made the admission as MPs voiced opposition to the Conservative plan to ban the substance pending further investigation into whether or not it is harmful.
Labour wants to make poppers exempt from a proposed banned list of substances on the grounds that prohibiting their use could cause harm, particularly in the gay community, by driving the sale of them "underground".
Outside the chamber, shadow home secretary Andy Burnham wrote a letter to Home Secretary Theresa May expressing his concerns about the proposed ban.
Speaking in the Commons during the report stage of the Psychoactive Substances Bill, Reigate MP Mr Blunt said: "There are some times when something is proposed which becomes personal to you and you realise the Government is about to do something fantastically stupid and I think in those circumstances one has a duty to speak up.
"I use poppers, I out myself as a popper user, and would be directly affected by this legislation and I'm astonished to find that it's proposing to be banned and, frankly, so were many other gay men.
"If I follow my own mindset reaction to this it simply serves to bring the whole law into disrepute.
"Choosing to ban this, which I have been using and I know has been used ... for decades, then respect for the law is going to fly out the window for people if that's the drug that they use.
"All the warnings that are contained within paragraph 43 of the select committee's report, particularly that from the Gay Men's Health Collective, saying it results in increased class A and B drug use and increased transmission of sexually transmitted infections is obviously going to happen, and driving the supply of these underground simply puts it in the hands of criminals."
Mr Blunt, MP for Reigate, labelled the policy "foolish" and warned people could be put into the "hands of the criminals" and suppliers who might seek to tempt them with other substances.
He said: "It is manifestly stupid to go down the path that we're doing.
"Let's have the evidence and then if the Government can then come forward with a case that can then convince the chairman of the Home Affairs Select Committee and his colleagues on that in due course, then we can have a discussion about this issue then."
Conservative David Davis, a former shadow home secretary, said the issue of supply seemed to be a "grey area".
He told Mr Blunt: "I understand it's intended not to victimise current users of this drug but it does put them in a position where they might be susceptible to blackmail if they are a public figure dealing with a criminal.
"So it does seem to me that it will criminalise people who it does not intend to criminalise."
Mr Blunt replied: "Indeed. I suppose I'm advertising the fact that I might be vulnerable to that.
"So I'm pleading with the House to then make sure I don't find myself caught in this particular situation.
"But given it relates to my own personal experience, and my experience as a minister for justice with a responsibility for offenders and offender management, I implore my colleagues to, at the very least, if they don't want to be seen to be voting against the Government, please don't be associated with putting this on the statute book.
"It's a real mistake and anything that can be done to accept amendment five would be the sensible thing for us to do and have a look at it again in due and considered time."
Amendment five calls for poppers to be exempted from the Bill.
Shadow home office minister Lyn Brown told MPs that poppers should be treated in the same way as alcohol.
She said: "If passed, this amendment will add poppers to the list of exemptions to the ban on psychoactive substances.
"Poppers would then be treated like nicotine, alcohol and caffeine – substances which we know to be psychoactive but we do not feel it judicious to ban."
Ms Brown said she was afraid that banning the products would "push their use underground and away from regulatory controls that currently exist".
"In short, we may do more harm by this action," she said.
"If after a review and further evidence it is proven that poppers are harmful and on balance a ban would be appropriate, we on this side will willingly review and test the evidence and if the case is proven, support a ban on these substances."
Ms Brown also outlined her belief that Government ministers had used poppers in the past to "keep going".
"They have been around for decades," she said.
"In fact they were created I think in the late 19th Century.
"In fact I understand that some ministers in this House at the despatch box have used them simply to keep going because they were prescribed at that time by their doctors.
"The reality is that if we ban them now and then un-ban them in four months, I think it would just create confusion."
Instead of forcing each new legal high to be individually banned as they are created and sold, the Bill creates sweeping new powers to make all psychoactive substances illegal with listed exceptions.
It bars the production, distribution, sale and supply of legal highs - imposing a seven-year prison term on convicted offenders.
Keith Vaz, Labour chairman of the Home Affairs Select Committee, said his committee unanimously recommended that poppers should not be banned.
Mr Vaz told MPs: "We said if there's evidence the Government brought forward to change that position and to change our view then of course they should be added to the banned substances.
"Indeed we say this - if there's any evidence produced to the contrary then poppers should be removed from the exempted list or controlled under the Misuse of Drugs Act."
He argued the amendment should be accepted, a Government review take place and then every MP will accept what the experts say about poppers - adding he would back a ban if the evidence shows the substance is harmful.
Mr Vaz noted: "To ban then un-ban sends a powerful message out to a section of our community that they are not being listened to and to experts who have given evidence to us that they are wrong."
In a letter to Mr Vaz's committee on Tuesday, Mr Penning indicated the Government could back down on its proposed poppers ban and add it to the list of exempt substances without the need for passing new laws.
The minister said the Home Office alongside the Department of Health would consider whether to exempt poppers from the blanket ban before making a decision.
He wrote: "The Government recognises that representations have been made to the effect that 'poppers' have a beneficial health and relationship effect in enabling anal sex for some men who have sex with men, amid concern about the impact of the ban on these men.
"In consultation with the Department of Health and the Medicines and Healthcare products Regulatory Agency (MHRA), the Home Office will now consider whether there is evidence to support these claims and, if so, whether it is sufficient to justify exempting the alkyl nitrites group (or individual substances in the group).
"Clause 3 of the Bill enables the Home Secretary, by regulations (after statutory consultation with the Advisory Council on the Misuse of Drugs and subject to the affirmative procedure), to add to the list of exempted substances in Schedule 1 to the Bill.
"The Government intends to complete such consideration in time to enable any such draft regulations to be laid before both Houses and approved before the summer recess should the Government conclude that a case had been made to include alkyl nitrites in the list of exempted substances.
"Subject to parliamentary approval of the Bill, it remains the Government's intention to bring its provisions into force from April."
Tory Mike Freer (Finchley and Golders Green) said poppers help LGBT couples achieve intimacy that would be more difficult without the drug's muscle-relaxing properties.
Mr Freer said it therefore has an important emotional and mental health benefit and raised the possibility of licensed sex shops selling the substance.
"Mr Vaz talked about anal sex," he said.
"That's quite a crude way of saying that poppers can facilitate through the relaxation of muscles.
"However the point I want to make - it isn't just about the physical side of relationships.
"If your relationship wishes to be as intimate as possible and poppers facilitates that, that is an important element into the emotional wellbeing of that couple.
"So if we're talking about the medicinal benefits we have to include the relationship benefits and the mental health benefits that the use of poppers in a relationship could bring.
"It is important that we don't start banning things on the basis of one or two incidents - it has to be a significant risk of significant harm to a significant number of people, otherwise we would be banning cigarettes and alcohol tomorrow."
But Mr Freer, who is Commons Leader Chris Grayling's parliamentary private secretary, said he would support the Government in applying the ban, insisting there must be empirical evidence before poppers are exempt.
"I have to say the Opposition have spoken a lot of sense", he said.
"However I will be supporting the Government because one of the things that concerns me is I want an exemption based on empirical evidence, so that if poppers are exempt by the summer recess as outlined in the response to the Home Affairs Select Committee, that exemption cannot easily be overturned at whim of a future Home Office minister, that exemption is based on empirical evidence whatever it says and on that basis I'll be supporting the Government on this particular issue."