Disenchantment among the British electorate with the three main parties is at a record high after 10 days of revelations about the expenses claims of the nation's MPs.

Two in five say they will refuse to vote or select one of the minor parties, such as the Greens or Ukip, rather than support the Tories, Labour or the Liberal Democrats, a ComRes poll shows.

The figures presented on the front page today are percentages for the entire electorate, and so include the 23 per cent who say they will not vote in the Westminster elections. They also include 17 per cent who will consider voting for a minor party – and that could prove a big opportunity for the Greens and Ukip at the forthcoming European polls, where they would be expected to do much better than in the first-past-the-post system.

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The 40 per cent for "none of the above" is compared with 31 per cent for the Tories, 16 per cent for Labour and 13 per cent for the Lib Dems.

Among those absolutely certain to vote, the figures are even more stark – 64 per cent back "none of the above". Of these, 54 per cent are unlikely to vote and 10 per cent back other parties. This would leave the Conservatives on 18 per cent, Labour on 10 per cent and the Lib Dems on 8 per cent, suggesting there may be a record low turnout at the next election.

On the traditional state of the parties measure, Labour slides five points on last month to another record low – 21 per cent – with the Tories also slipping five, though well out in front on 41 per cent. The Lib Dems remain at 18 per cent. In an election, this would give David Cameron a majority of 152.

The slump of Labour and the Tories since the ComRes poll for The Independent last month underscores how the main parties are being punished for the expenses scandal. And a supplementary question asked of voters suggests that 43 per cent will consider voting for a minor party in the European elections next month. Other polls suggest that the Greens are set to double their 6 per cent of last time round.

Andrew Hawkins, chief executive of ComRes, said: "I can't remember any time when the minor parties were at anything like this level."

In an attempt to regain the initiative and restore trust, Gordon Brown will today issue a veiled threat to ministers whose expenses are under investigation that they could be sacked. The Prime Minister warns that any minister who is found to have "morally" or technically broken the rules "will not serve" with his government. He adds that Labour MPs found to be cheating will be deselected.

The Metropolitan Police has announced that it will this week consider launching criminal investigations into MPs' expenses claims. Downing Street sources refused to comment on the "scoping" inquiries into several MPs, including Chancellor Alistair Darling, Transport Secretary Geoff Hoon and the employment minister Tony McNulty.

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The Speaker, Michael Martin, will also come under intense pressure to carry the can for the scandal, with friends suggesting he might announce his intention to stand down before the next election to try to appease critics. A motion of no confidence is expected to be tabled by MPs as early as tomorrow. His former media adviser, John Stonborough, told The Sunday Times last night that Mr Martin ruled with a "reign of terror" that allegedly held up a solution to the expenses crisis.

Yesterday Martin Bell, the anti-sleaze campaigner, suggested he might stand for election against an MP hit by the scandal, possibly the Speaker. There were reports last night that even the Queen has made clear to Mr Brown her unhappiness at the crisis. And an investigation by the IoS has discovered that Britain's MPs are taking advantage of another allowances "loophole" that lets them channel taxpayers' money into the network of local constituency associations around the country. More than 100 MPs are using expenses to pay their often impoverished constituency parties thousands of pounds a year for facilities and services such as rent and secretarial help. The MPs, who include Mr Cameron and nine members of his Shadow Cabinet, say they are paying for legitimate business services and that the arrangements have the blessing of House of Commons authorities.

In the ComRes poll, 50 per cent disagree with the statement that "most MPs are honest and have been let down by the greed of a minority", while 46 per cent agree. Six out of 10 voters believe Mr Cameron has dealt with the expenses issue better than Mr Brown.

Yet there is bad news for Labour MPs hoping for a fresh start under a candidate such as Alan Johnson, with just 32 per cent of people agreeing that the Health Secretary would be a better Prime Minister than Mr Brown.

The Sunday Telegraph today printed more revelations, including the expenses of the Tory MP Julian Lewis, who claimed more than £7,000 for redecorating his second home and installing new kitchen appliances. The MP for New Forest East denied any wrongdoing and said he would be "astonished" if an internal party audit ordered by Mr Cameron would judge any of his claims unreasonable and demand he return the cash.

Labour MP David Chaytor became the second in his party to be suspended, following Elliot Morley's downfall last week, after he admitted claiming £13,000 in mortgage interest payments for a mortgage that had been repaid. Mr Chaytor said he had made an "unforgivable error" and apologised unreservedly.

A ComRes poll of European voting intentions for the Sunday Express, commissioned by Ukip, put the Tories on 28 per cent, Labour on 20 and the Lib Dems on 14. Ukip were on 15, the Greens on 11 and the BNP on 4 per cent. And a BPIX/Mail on Sunday survey of general election voting intentions put the Tories on 42 per cent and Labour down at 20 per cent.