Senior Conservative backbencher Sir Malcolm Rifkind has declared it is "simply unrealistic" to believe MPs can survive on "simply £60,000" a year - over twice the average national wage - without looking for extra income.
The former foreign secretary's remarks come in his first broadcast interview since an undercover investigation by the Daily Telegraph and Channel 4 Dispatches suggested that he, and senior Labour MP Jack Straw, were prepared to use their positions and contacts to benefit a private company in return for payments of thousands of pounds.
The two senior MPs were secretly filmed by reporters claiming to represent a Hong Kong-based communications agency called PMR which was seeking to hire senior British politicians to join its advisory board.
At one meeting, Straw is said to have described how he operated "under the radar" to use his influence to change European Union rules on behalf of a commodity firm which paid him £60,000 a year.
He was also said to have claimed to have used "charm and menace" to convince the Ukrainian prime minister to change laws on behalf of the same firm.
The meetings to discuss possible consultancy work were said to have taken place in his House of Commons office - a potential breach of Commons rules.
Sir Malcolm, who chairs the parliamentary committee which oversees Britain's intelligence agencies, was said to have claimed that he could arrange "useful access" to every British ambassador in the world because of his status.
While members of both the House of Commons and the House of Lords have been caught up in so-called "cash-for-access" scandals in recent years, Straw and Sir Malcolm are by far the most prominent figures to face such claims.
In his first broadcast interview since reports emerged, Sir Malcolm told BBC Radio 4’s Today Programme that it was “misleading” and “silly” to tell undercover reporters, in remarks that will be broadcast tonight, that he was “self-employed” and they would be “surprised how much free time I have”.
The Tory MP insisted the "very serious allegations" were "unfounded" and he would be "hugely irritated and angry" when he watched the Channel 4 show tonight about his meetings with fake lobbyists.
Sir Malcolm told the Today Programme that over 200 MPs have “various business interests” outside of Parliament and said whether that should be allowed was the key question in the row.
“Now some people disapprove of that and maybe the Labour Party’s going to disapprove of that. But many of the public have got a different view, he said.
“Not of all of them but many say ‘actually we don’t want full time politicians. We want Members of Parliament that have some outside experience of the wider world.’ And that is a perfectly reasonable proposition.
“I think also if you’re trying to attract people of a business or professional background to serve in the House of Commons and if they’re not ministers it is quite unrealistic to believe they will go through their parliamentary career being able to simply accept a salary of £60,000."
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Meanwhile, Jack Straw, who is standing down at the election, said he had agreed to suspend himself from the parliamentary Labour Party and refer himself to the Parliamentary Commissioner for Standards despite insisting he has done nothing wrong "because of the way this appears".
He told Today: "I'm mortified by the fact that I fell into this trap set by a very skilful journalist from Channel 4 and it was a very skilful trap but I fell into it.
"And, inevitably, if you have what you think is a private conversation where you trust the person, or people, you are talking to, you use language not that's necessarily wrong but could be taken out of context."
The former Labour foreign secretary insisted he had been "absolutely scrupulous" in observing all the rules, including on outside interests.
"This discussion with this bogus Chinese Hong Kong company was not about what I was going to do as a Member of Parliament. It was all about what I might do once I had left the House of Commons on May 7."
Asked why he had not waited until after the election, he replied: "Well, I should have done, is the answer. It would have saved a fantastic amount of time and trouble and what I had hoped was the last five or six weeks of time in the House of Commons being a rather valedictory way through being caught up with all of this.
"Of course I very much regret the fact that I saw these people."
Straw said he had had "five or six approaches" over the last 18 months about what he would like to do when he has finished.
"Yes, I'm interested in earning money but above all what I'm interested in is doing things which would engage my brain and use whatever skills and knowledge that I've got." He said all but one had "gone nowhere".