Lord Holme, the Liberal Democrats' campaign manager, said that local activists in Tatton were seeking out a "credible, independent anti-corruption candidate", following Labour's decision to stand aside in favour of a non-party challenger for Mr Hamilton.
But the Tories are hoping to use today's launch of their manifesto to divert attention from sleaze, with a number of initiatives including a pounds 1bn tax bonus for married couples.
According to last night's Tory spin, the "revolutionary" tax dividend, could deliver about pounds 18 a week to two million married couples when one of the partners stays at home and diverts a personal tax allowance to the working spouse.
The threat to mount an independent challenge in Tatton was given added impetus yesterday by the Prime Minister's claim that he would not act against Mr Hamilton, and by the local party's support for the beleaguered candidate.
Alan Barnes, the Tory association's chairman, said he welcomed Mr Major's "belief, in principle, that people against whom allegations are made are innocent until proven guilty".
A growing list of people who might be considered as anti- corruption candidates being bounced around Westminster included the Virgin boss Richard Branson, Frances Lawrence, widow of the murdered headmaster Philip Lawrence, Judge Stephen Tumim, the retired HM inspector of prisons, the business guru and author Charles Handy and Elspeth Howe, wife of Lord Howe and chair of Opportunity 2000, which seeks to put more women in business.
Defiantly using the first daily press conference of the four-week election campaign to field questions about Mr Hamilton and sleaze - in a clear attempt to kill the issue once and for all - Mr Major squarely attacked all suggestions that Mr Hamilton should have to stand down before any findings of guilt or innocence had been reached on the cash-for-questions allegations levelled against him.
"I am not going to bow to the witch-hunt mentality of saying that anybody who faces unsubstantiated charges must leave public life," Mr Major said. But he also gave the strongest possible hint that he was unhappy with the ability of local party associations to stand up to the party leadership - and refuse to dump candidates who were embarrassing the national party.
"They have to work with a candidate, they have to support him or her in their campaigns and beyond, and it has always been their position," he said. But he then added: "We may have to look at that at a later stage in the events of the Nineties." Mr Hamilton, who remained inside his home yesterday, was not saying anything about the future that was dominating the first full day of election campaigning.
Lord Holme said that the Liberal Democrat candidate, Roger Barlow, was still in place, and there was no question of him standing down until a suitable person had been found. Mr Barlow and the Labour candidate, Jon Kelly, will both remain in place as prospective candidates until 8 April, when the Tatton Conservatives will make a final decision on whether to adopt Mr Hamilton as the official candidate.
Gordon Brown, the shadow Chancellor, said Mr Major had moved the debate on by putting his weight behind Mr Hamilton's candidature. "John Major's statement today about Tory candidates has introduced a new element into the campaign in Tatton where a Conservative MP with clear and admitted financial wrongdoing is standing," he said.
"It is now clear that after a weekend in which senior Tories called for Mr Hamilton to stand down, reportedly at the behest of Mr Major, the Prime Minister is now putting the whole authority of his leadership behind backing the endorsement of Mr Hamilton."
t The Conservatives are gaining on Labour, according to a newspaper opinion poll published today. The Guardian/ICM poll shows Labour on 46 points, down two from last month, the Conservatives on 32, up two, and the Liberal Democrats on 17, up one. 1,200 people were questioned over Easter weekend.Reuse content