David Cameron has been criticised by stalking victims for reneging on his pledge to toughen the law.
The Prime Minister announced at a reception last week that stalking was to become a specific criminal offence.
He insisted that existing legislation was not "good enough or strong enough" to deal with the "dreadful" problem.
The changes came after a long campaign by the Plaid Cymru MP Elfyn Llwyd, who welcomed the changes when they were announced. But Labour described the new law as "half-hearted", claiming that proving a "fear of violence" in the terms laid out would be tricky for the police.
After studying the measures proposed by the Government, campaigners have concluded they will make little difference.
The changes would create one stalking offence that was triable only by magistrates - with a maximum sentence of six months.
A second more serious offence could attract heavier punishments in crown court, but the prosecution would need to show the victim suffered "fear of violence" - something critics say is very difficult to prove.
Claire Waxman, who was awarded damages after the authorities failed to protect her from a stalker, met the premier at the Downing Street event on Thursday.
"It seemed positive. He seemed to have a real handle on what needed to take place," she told the Press Association.
"I just don't know what has happened since that meeting. This is pretty much what we have already got. They have just added in the word 'stalking' (to anti-harassment legislation).
"It is pretty disappointing to say the least.
"Maybe I am naive but I thought if a Prime Minister agrees to something and commits to it, then it would happen."
Tracey Morgan, who was subjected to an eight-year reign of terror by a work colleague, also met Mr Cameron on Thursday. "I felt he listened and took in what we were saying, but looking at the proposals I wonder, what's the point?" she said. "It is disappointing really."
Harry Fletcher, assistant general secretary at probation union Napo, which has been campaigning for stronger legislation, said: "The stalking reforms are welcome but do not give adequate and proper protection for victims.
"The Government must recognise that stalking results in psychological harm and wrecks lives.
"Limiting psychological effects to the magistrates court will mean that sentences are woefully short and the perpetrators will receive no treatment or even rehabilitation and as a consequence there will be repeat victimisation."
Laura Richards from charity Protection Against Stalking added: "We welcome the creation of a new offence of stalking, however stalking being named is the only thing that is 'new'.
"It has been tacked on to the current Protection from Harassment Act 1997 and is a rehash of what we know does not work.
"This is wholly inadequate and the new legislation needs to go further and take account of all the evidence from the Victim's Voice Survey, the Parliamentary Inquiry and Scotland."
The Government's stalking reforms are due to be considered when the Freedoms Bill gets its third reading in the Lords on Monday.
Labour has tabled amendments allowing for psychological damage to be taken into account as well as fear of violence.
Another change would permit magistrates to refer serious cases to a higher court.
The Opposition leader in the Upper House, Baroness Royall, said: "The real problem is that the Government is looking to retain the worst features of the existing law.
"While the words look fantastic, and at first glance you think, 'Good, the Government's doing exactly what it should', in fact they are not."
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