I've known Sir Malcolm Rifkind for nearly 30 years and always thought of him as one of the few genuinely honourable Honourable Members.

So it was with dismay that I learned he'd been implicated in the latest cash-for-access sting. I was even more dismayed hearing him spend all day digging himself deeper into the pit of dishonour.

It's not clear which was worse: the revelations about Jack Straw and Sir Malcolm's lucrative moonlighting or the way they tried to rationalise their conduct. Anyway you look at it, being prepared to take £5,000 a day from a dodgy Chinese company for parliamentary services is outrageous.

But Mr Straw said it was alright because he's leaving parliament soon. Yet he admitted he'd already been doing services "under the radar" for private companies while an MP at the above rate. Anyway, as a former Labour foreign secretary, he can expect near-automatic elevation to the House of Lords which, the last time I looked, was also part of parliament.

Sir Malcolm Rifkind went even further down the road of incomprehensible self-dishonour. He was filmed saying that he "didn't have a salary" and that he was "a small businessman". This will come as news to his Kensington and Chelsea constituents who were under the impression that he was working for them at a remuneration of £82,000.

Sir Malcolm receives £67,000 for being an MP, which would already put him in the top four per cent of salary earners in Britain. But he also receives £15,000 for being chairman of the Intelligence and Security Committee. Yet he told the cameras that he spent much of his time wandering about and reading.

No, you really couldn't make it up. Here was a guardian of the nation's security apparently offering himself for hire to a Chinese company which, since China is a communist dictatorship, would likely have direct links to the Chinese state. You don't have to be James Bond to connect the dots here.

Sir Malcolm went into a lather of righteous indignation on the Today programme, denying any impropriety and attacking the Daily Telegraph for misleading the public. But within hours he was suspended from the Conservative Party in parliament and effectively disowned by the Prime Minister, who declined to express confidence in him.

For his part, Ed Miliband hung Jack Straw out to dry saying he was "disappointed" and that, in future, Labour MPs were going to be barred from holding lucrative directorships and consultancies.

At least, I hope that's what he was saying. You always have to run politicians' statements on cash for access through a Grade-A bull***t detector to check if they're actually saying what they seem to be saying. Most voters are probably under the misapprehension that parliamentary payola had been outlawed years ago and that MPs were expected to do the job they are paid to do.

When I was working in Westminster I covered the Lord Nolan sleaze inquiry sessions in 1994-5 following the original cash-for-questions scandal. The central issue was the same: MPs for hire. And Lord Nolan made it absolutely clear back then that the public had had it with this kind of behaviour. Yet, 20 years on, we are still here.

This time, however, I suspect action will finally be taken. Mr Miliband has called for a cap on all MPs' outside earnings of 10-15 per cent. With a general election imminent, David Cameron is going to have to follow suit, or face the consequences. As Sir Malcolm pointed out, 200 MPs declare outside earnings and most of the big earners are Conservatives. Cash-for-access is especially toxic for the Tories.

And of course it is access that these outside firms are really buying. They aren't going to pay £5,000 a day just to have readings from Hansard. As Mr Straw made clear, it is the "under the radar" work that former ministers in particular can offer through their extensive contacts.

But their contacts book has been bought with public money. They shouldn't have the right to sell it off to the highest bidder. Influence-peddling in the corridors of power should be seen for what it is. If MPs need experience of "the real world" they can spend time in a law centre. Or better still, in Poundland.