Shadow Commons leader Alan Duncan has apologised "unreservedly" after he was secretly filmed complaining about MPs' pay and expenses.
The Tory MP was heard to say MPs were being treated badly after the expenses scandal and "have to live on rations".
Mr Duncan said the remarks, made to film maker Heydon Prowse of Don't Panic magazine, were meant as a joke.
But he added: "The last thing people want to hear is an MP whingeing about his pay and conditions."
He told BBC News: "It is a huge honour to be an MP and my remarks, although meant in jest, were completely uncalled for. I apologise for them unreservedly."
The film shows Mr Duncan using strong language as he complains MPs have to "live on rations" and get treated badly - after being questioned about his expense claims.
It appears to show Mr Duncan on the House of Commons terrace saying: "No one who's done anything in the outside world or is capable of doing such a thing will ever come into this place ever again the way we're going."
This was at the height of the scandal, but the attitude was that it was all a bit of a joke
Heydon Prowse, editor Don't Panic
He then appears to add: "Basically it has been nationalised. You have to live on rations and you are treated like shit."
Mr Duncan is not in vision when he makes the remarks but his voice can clearly be heard.
He is also quizzed by Mr Prowse about his expenses claims for gardening.
The Rutland and Melton MP says: "I spend my money on my garden and claim a tiny fraction based on what is proper. And I could claim the whole bloody lot, but I don't."
He then adds: "About £2,000 a year and this was £1,000 a year on expenses, you know. It's just, I'm afraid the world has gone mad."
The film was posted on the Don't Panic website at the end of July. It was removed from the site but has now been republished.
Mr Prowse was invited to the Commons by Mr Duncan after he was filmed digging a pound-shaped hole in the MP's lawn in protest at his expenses claims. The video clip of Mr Duncan's lawn became a hit on YouTube.
Mr Prowse said he took the secret camera along to the meeting in July in the hope of catching Mr Duncan out but he regretted getting him into trouble because he found the Conservative MP to be a "very charming and generous guy".
But he said he thought it was important to expose the attitude of politicians towards the expenses scandal.
He said: "What we captured was the general prevailing attitude in the Commons that he didn't take the whole expenses scandal particularly seriously.
Lord Mandelson: "'Alan Duncan is very fond of speaking a good game publicly'
"This was at the height of the scandal, but the attitude was that it was all a bit of a joke."
Mr Prowse describes himself as a film maker rather than a campaigner and he says his magazine carries a mixture of arts and politics.
As shadow Commons leader, Mr Duncan has overseen much of the Conservative response to the expenses row and has said he would pay back more than £4,000 of expenses.
Mr Duncan, a former oil trader, became an MP in 1992 and has held a string of front bench roles.
The MP's remarks have been seized on by his political opponents.
Business Secretary Lord Mandelson, currently standing in for Prime Minister Gordon Brown who is on holiday, told the BBC News Channel: "Alan Duncan is very fond of speaking a good game publicly but in private talking and acting quite differently, so I am not surprised he has been found out."
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