Charles Clarke has launched a scathing attack on Fleet Street's "pious and hypocritical" approach.

Writing in The Times, the Labour chairman accuses newspapers of bringing democratic politics into disrepute.

He claimed that some papers had taken it upon themselves to become the unofficial opposition.

Clarke's outburst was backed by Downing Street who said the media had become too obsessed with pursuing false "sleaze" stories.

"What Charles is saying, and what we completely agree with, is that it's important that judgments are made on the basis of fact," said a spokesman."No-one is saying the media doesn't have a legitimate role to scrutinise, to criticise, to question.

"But if you look at all these stories, the so-called sleaze and donor stories for example, despite the great brouhaha we have had about all of them, nothing improper has been shown to have happened."

Clarke said the media is using spin rows as "proxies for attacks on the government... in the absence of any effective Conservative opposition".

"I believe that much of the criticism is pious and hypocritical, sometimes entirely manufactured, coming from parts of the media which themselves have done their best to bring democratic politics into disrepute," he wrote.

Clarke tore into the methods used by the media to unearth stories.

"The print and broadcasting media have enormous investigative resources and immense databases, which do not rely on public statements but include intrusive investigations into personal lives, even financial affairs," he claimed.

"It is the media, and not any political party, which camp out on people's doorsteps, duplicitously seek personal financial information and 'expose' personal sexual peccadilloes."

Taking up issues that have dominated press headlines over the last week, he called on the media to put its house in order.

Clarke said special advisers had been an established part of the political landscape for decades.

He rejected claims by Plaid Cymru that party officials were investigating the private lives of opponents.

"We have no investigative resources of that type. We do not need them and would never think it appropriate to use them," Clarke said.

He also hit back over the issue of party funding, claiming that the media reports into donations by Lakshi Mittal, Richard Desmond and Bernie Ecclestone had no substance behind them.

"In every case serious misconduct has been alleged, at great volume, but it has never been demonstrated, for the simple reason that it does not exist," he said.

Clarke claimed the media had a duty to maintain standards and called for more open reporting of the facts.

"Politicians have a duty to maintain high and transparent standards," he said. "I argue that the media also have the responsibility to report politics fairly - based on the facts and in a balanced way - which reflects true political differences, and not manufactured misconduct."

But his remarks have been dismissed by opposition parties who have hit out at the government's reputation for media manipulation.

Shadow cabinet office minister, Tim Collins, accused Clarke of "whinging and moaning".

"The Labour Party is being paranoid. It is typical of New Labour that when criticised they seek to attack their critics rather than accepting they have done something wrong and trying to put it right," he said.

Liberal Democrat chairman, Mark Oaten, conceded that the media's approach had become sensationalist but claimed Labour's spin tactics for the shift."Clarke is right to say that the reporting of politics is becoming increasingly sensationalist, but given their track record over the last five years, Labour only have themselves to blame," he said.

"Sorry appears to be the hardest word for the government. If they are to avoid the reputation with which the last Conservative administration ended their time in office, it is they who must change.

Oaten said Labour's pre-government dalliances with the media were returning to haunt the government.

"Labour wooed the media in 1997 to gain power and now it seems their honeymoon is over. Surely Mr Clarke is aware that in politics if you live by the sword you die by it as well."