Bitchy. Gossipy. Deadly. Inside the whispering world of Westminster

Psst! Want to know how they shafted Filkin? Or what they think of Blunkett? Then join Jo Dillon for a pint of bitterness or a cup of conspiracy in the tea room and bars of the House of ill-repute

Sitting in the Commons tea room with a plate of teacakes and a steaming pot of Earl Grey, a cluster of MPs enjoy a bit of well-earned relaxation. Meanwhile, in the Strangers' Bar, friends share a bottle of Chardonnay or a couple of pints after work. And leaning against the wood panels, colleagues chat in the Commons corridors.

They are all familiar scenes at the Palace of Westminster. But the civilised social facade disguises a world fuelled by bitching and backbiting, where careers and reputations can be made and broken by a snide remark or an unsubstantiated story.

Ask Elizabeth Filkin. After three years as the Parliamentary Commissioner for Standards – a lonely job at the best of times – Mrs Filkin has thrown in the towel. She tendered her resignation as the guardian of the probity of Parliament, blaming a "whispering campaign" waged by "powerful individuals" within the House of Commons. But this was no orchestrated, organised campaign against her. Rather, it was a tearoom chat between the MP for Disgruntled East and the member for Sympathetic West, egged on by the MP for Stirring South and joined by the member for Don't Leave Me Out North.

Mrs Filkin's critics claim that she, by responding to gossip and allowing rumours to be published simply on the basis that she was to investigate them, helped perpetuate this culture of tittle-tattle. As the father of the House, Tam Dalyell, said: "For an MP, her or his reputation is all-important and if it's sullied it's difficult to de-sully it."

Nevertheless, Mrs Filkin was fearless in the politicians she took on: Peter Mandelson; the Deputy Prime Minister John Prescott; the Secretary of State for Northern Ireland, John Reid; the millionaire former paymaster general, Geoffrey Robinson; the former Europe minister, Keith Vaz; former prime minister John Major; and former Tory leader William Hague among them. They are powerful men with powerful friends. And yet many MPs seem to thrive in a Parliamentary culture that treats the reputations of colleagues lightly. Little goes on at Westminster that the gossip-mongers, aided by political diary columnists, consider off limits.

It seems that as long as it's a story, no one actually cares whether it's true or not. Labour MP Paul Marsden claimed last week that he had suffered "verbal and physical intimidation" at the hands of Government whips in the Strangers' Bar.

The alleged incident took place at 3am. It was in the papers the next morning. And by that evening, what appeared in the media had been exaggerated beyond recognition, without any thought for the reputations of the alleged perpetrators.

Far from being just idle chat, some of the gossip is deliberately engineered to diminish the standing of individuals. David Blunkett, the Home Secretary, who only a fortnight ago was predicted to be the next Labour leader, was being roundly damned by allies of Gordon Brown, the Chancellor, as his anti-terrorism bill suffered defeats in the House of Lords. "We are finally seeing that Mr Blunkett is a municipal politician of limited ability," one said.

The who's up/who's down conversation is a favourite of politicians and parliamentary journalists. Stephen Byers, the Secretary of State for Transport, walked into the Strangers' Bar on two successive nights last week – a reasonably rare occurrence. "That's a clear sign that his career's fucked," mumbled one helpful colleague.

When they're not deciding by committee the fate of unwitting ministers, the gossip squad busies itself with devouring people's private lives. Less well-liked MPs are censoriously branded "thirsty" for enjoying the odd drink – over a few pints.

The Strangers' Bar, the dining rooms and the Pugin Room, overlooking the Thames, are rife with ill-informed speculation about people's sex lives. Rumours that someone "bats for both teams" or is a "complete shagger" are the meat and drink of political small talk. Broken marriages and shattered lives attract little sympathy. They're just another bone to chew on.

Being seen to be "in the know" – however malicious or petty the subjects you are claiming to know about – is all. As one MP said, having fallen foul of the diary columns on more than one occasion: "I've never known anywhere like this. It's a nightmare."

And yet MPs lament the poor public standing of their profession while allowing this culture – which they know undermines the work of committed, assiduous politicians – to flourish. The problem is not simply malicious gossip; lives and careers are destroyed in a few words.

Whether they are politically ambitious tacticians, self-protecting cliques or simply nasty gossips, the only achievement of the House of Commons "whisperers" is to create a political culture the public despises and to undermine themselves and an already degraded Parliament.