Disaster for Gordon Brown as Labour falls below Lib Dems in new poll Gordon Brown has suffered a devastating blow with a new opinion poll showing Labour's support in a general election falling behind the Liberal Democrats for the first time in 22 years.

Gordon Brown has suffered a devastating blow with a new opinion poll showing Labour's support in a general election falling behind the Liberal Democrats for the first time in 22 years.

The ICM poll for The Sunday Telegraph is the worst possible news for the Prime Minister as he enters his most important week since taking power with Labour expecting a hammering in Thursday's local and European elections.

The results, which show Labour has suffered particularly badly from the MPs' expenses scandal in voters' eyes, are certain to ratchet up speculation that Mr Brown will face a leadership challenge in the next few weeks.

Asked who they would support in a general election, only 22 per cent of voters back Labour, with the party slumping behind both the Conservatives on 40 per cent and, crucially for Mr Brown's future, the Liberal Democrats who are on 25 per cent.

The last time Labour was in third place in any poll in a "general election" question was in 1987 - when the party was reeling from defeat in a by-election held in Greenwich and hard-left local councils were tarnishing its reputation across the country.

The results when voters were asked who they would support in Thursday's elections to the European parliament are no better for Mr Brown.

Labour again comes third with just 17 per cent, down from the 22.5 per cent the party achieved in what was judged a poor performance in the last set of such elections, in 2004.

The Conservatives lead in today's poll with 29 per cent, while the Lib Dems are on 20 per cent.

The United Kingdown Independence Party (UKIP), which has achieved scores rivalling Labour's in recent polls, only gets 10 per cent and is beaten into fifth place by the resurgent Greens, who are on 11 per cent.

The British National Party (BNP), meanwhile, is flatlining on 5 per cent.

Although predictions of vote share at European elections are notoriously difficult, due in part to low turnout, Labour is already braced for a heavy defeat.

Ed Balls, the Schools Secretary, has already conceded the party will perform badly.

If Labour loses control of the four county councils it is defending on Thursday and gets under 20 per cent of the vote in the European elections, Mr Brown could face a challenge from within his Cabinet - with Alan Johnson, the Health Secretary, set to emerge as his likeliest successor.

The Prime Minister is thought to be planning a sweeping Cabinet reshuffle next week in an attempt to reassert his political authority.

A report in Saturday's Daily Telegraph suggested he was considering some sort of power-sharing deal with the Liberal Democrats, including bringing leading Lib Dems such as Vincent Cable, the party's Treasury spokesman, into the government.

Nick Clegg's party has emerged relatively well from the MPs' expenses scandal.

When asked by ICM which main party had been most damaged, just 2 per cent said the Lib Dems, compared with 54 saying Labour had come out worst and 13 per cent claiming the Tories were the most damaged.

Some 25 per cent say all three main parties have been equally damaged.

Just over a third of voters (35 per cent) want a general election now, following David Cameron's call for one, while a further 19 per cent want an election in the autumn - making 54 per cent in total who want to vote in a new parliament this year.

Some 39 per cent want Mr Brown to wait until next year before going to the country, which he must do by June 2010.

In its general election finding, Labour's score of 22 per cent is the lowest ever level of support recorded for the party since the company started regular polling in 1984.

Senior Labour sources warned of the dangers of protest votes being levelled in anger at the government but which would only benefit "unrepresentative" minor parties.

Mr Brown is expected to launch the latest stage of his fightback against sleaze allegations in television interviews on Sunday.