The shake-up could see close links with the Liberal Democrats established and even the inclusion of senior Lib Dem figures such as Vince Cable in the government.
According to reports, Brown's team is looking at a "game-changing" reshuffle after
the election and not just the simple reshuffle that often follows poor poll results.
Constitutional reform, including the possibility of using proportional representation in elections, is said to be favoured by as many as half the cabinet.
The need for action was underlined by a Populus Poll published yesterday which asked people how they would vote in this week's polls. The replies suggested that over the past three weeks, Labour support had fallen by nine points to 16 per cent.
The Tories dropped four points to 30 per cent, while the Lib Dems fell eight points to 12 per cent.
UKIP were the main party to benefit from the slump, rising from 13 points to 19 per cent – overtaking Labour for the first time. The Greens rose five points to 10 per cent and the BNP went up three points to 5 per cent.
When the sample was asked about their voting intentions for the General Election, Labour fell by five points to 21 per cent while the Tories went up two points to 41 per cent.
Tellingly, 62 per cent of those surveyed believed that the Prime Minister was most damaged by the whole expenses fiasco compared with just 5 per cent who thought that Cameron was.
Just 14 per cent believe Labour is likely to win the next General Election outright compared with 51 per cent, who think the Tories will win.
Labour's desperation to distance itself from the expenses row is illustrated by a blueprint for a letter that has been issued to European candidates.
All candidates have been advised of the form of words they should use to attempt to empathise with voters when writing about the expenses issue.
The letter, obtained by Scotland on Sunday, acknowledges "how angry people are with Westminster politicians". It advises candidates to say: "I suspect you are as fed up as I am as day after day more stories come out showing greed and in some cases, serious wrongdoing.
"I would like to echo Gordon Brown's words – that I am sorry that the political system has let you down. And as for the media reports that a Tory MP is blaming his constituents for his expense claims and thinks that 'we're all just jealous' is unbelievable."
In an attempt to pin the expenses scandal on the Tories, the letter was referring to the Conservative MP Sir Anthony Steen, who declared that the public had no right to "interfere" with his private life after it emerged that he had claimed for the treatment of 500 trees in the grounds of his house.
Steen defended himself saying: "I've done nothing criminal, that's the most awful thing, and do you know what it's about? Jealousy. I've got a very, very large house. Some people say it looks like Balmoral."
