Five years after the original scandal, two more highly experienced politicians were secretly recorded by undercover reporters in a sting that has again led to allegations of 'cash for access' .

This time it is former Foreign Secretaries Sir Malcolm Rifkind and Jack Straw at the centre of the storm.

Both men have referred themselves to a parliamentary standards watchdog and insisted that they had done nothing wrong.

Both also toured the radio and television stations to protest their innocence, although Mr Straw did suggest he had been guilty of stupidity.

The documentary Politicians For Hire, by Channel 4's Dispatches and The Telegraph has set shockwaves through the Commons, just months before the General Election.

It followed the same format to a similar investigation five years ago on the eve of the 2010 election.

That led to an inquiry while two of the politicians involved former defence secretary Geoff Hoon and former transport minister Stephen Byers were banned from parliament for five and two years.

This time undercover reporters who set up a fake communications agency, PMR, based in Hong Kong and backed by a fictitious Chinese businessman, recorded Sir Malcolm saying that he was 'self-employed' and discussing his usual fee of "somewhere in the region of £5,000 to £8,000" for a half a day's work.

He told them : "I am self-employed. So nobody pays me a salary, I have to earn my income, but when I'm not doing something I can do what I like".

On money he said: "One sensitive issue, but I have to mention it. You mentioned there would be obviously remuneration.... I would simply give it as an example, but when I did a series of presentations on the Middle East and that was usually something in the order of... I mean it wasn't a whole day, it was usually a whole morning or an afternoon and that was somewhere in the region of £5,000 to £8,000 something of that kind."

He also suggested that he could find out information, saying: "In my own case I could write to a minister... I wouldn't name who was asking but I would say I've been asked to establish what your thinking is on X,Y, Z. Can you tell me what that is?... But if it's an area of...they may be reluctant."

He also makes clear the limitations of what he can offer: "You cannot give privileged information to one private citizen or a company that is not available to others. Because why should they? There is no benefit from their point of view, and they will simply be very severely criticised. But there is an awful lot of information which is not secret which if you ask the right questions you'll get the answers. "

Sir Alistair Graham, a former chairman of the Committee on Standards in Public Life, said that if Sir Malcolm did write to a minister in the way "that would be a clear breach of the code of conduct".

In response to the allegations Sir Malcolm said he had never and would never undertake lobbying as an MP on for a fee.

He also denied being an 'MP for hire', sayiing: "That is untrue...There was no suggestion that I was being approached as an MP...(the) approach to me was because of my previous experience as a Minister... Ambassadors tend to respond not because I am a current MP but because I was Foreign Secretary."

Mr Straw, who unlike Sir Malcolm is standing down from the Commons in May, and who has been tipped as a future peer, was recorded after the undercover reporters told him that that PMR was looking for people to join its advisory board.

He told them he was an adviser to a firm of commodity traders called ED&F Man, and that when EU sugar regulations were hampering its business, he went to see "the relevant director general and his officials in Brussels and we got the sugar regulations changed... the crucial thing about this, it's all, it's public that the regulations have been changed, but the best way of dealing with these things is under the radar."

Mr Straw added"I'm well aware of the fact that I'm bringing my name - all right - I get that. But it's what it is you want from me, what I can offer you, could do for, what's the time commitment? Those things."

But he added that he would not take on the role while he was an MP.

However, he added: "I could end up in the House of Lords, so you're aware - you may have seen that...speculation in the paper at the moment - no one has said anything to me officially. But the rules there are different and plenty of people have commercial interests there."

He also took the reporters on a tour of parliament.

In response to the allegations, Mr Straw said: "I made clear from the outset that I was not available for any work until after I stood down as a Member of Parliament.

"Due to my other parliamentary commitments and to save time for further such work, I met the individuals in my parliamentary office.

"We had a general discussion about work I have done on a consultancy basis for another company.

"All of my outside paid work is fully and properly declared under rules that apply to MPs.

"I have also sought specific guidance from the Office of the Advisory Committee on Business Appointments (of former ministers) before undertaking projects."

He added that he was confident he did not breach any parliamentary rules "in substance or in spirit."