The battle to become Tory leader descended into abuse and recrimination yesterday when two of the candidates said a victory for Kenneth Clarke would split the party.
Bitter exchanges coincided with claims that front-runner Michael Portillo repeatedly feuded with William Hague in the run-up to last month's overwhelming election defeat.
The in-fighting has been fuelled by the momentum gathering behind Mr Clarke, who antagonised opponents yesterday by claiming the party wasted four years in opposition with its obsession over Europe.
The former party chairman Michael Ancram, also hoping to capture the support of centre-left Tory MPs, retorted: "To talk blandly about four wasted years is a real insult to all those who carried the Conservative standard at the last election on a number of policy areas on which I hope we can build.
"I am coming into this leadership campaign, unlike Ken, not saying everything has been wrong, and, not like Ken again, saying I have a policy which is going to divide the party."
The right-wing contender, David Davis said he found it "difficult to imagine" how Mr Clarke could unite the party.
He said: "Ken has to answer how he leads a party, the majority of whom disagree with him on a central issue. He's got a difficult job 85 per cent of the party believe we should not join the euro. He disagrees."
Mr Clarke's supporters were buoyed by a survey in The Independent last week revealing he was the preferred choice of grassroots activists.
The former Chancellor admitted yesterday his greatest challenge could be to persuade overwhelmingly Eurosceptic MPs to put him on the shortlist of two candidates presented to the party's 300,000 members.
Baroness Thatcher may intervene in the contest by endorsing Iain Duncan Smith, the shadow Defence Secretary.
In what his supporters hope will be a decisive boost for his campaign, she is expected to make plain her preference if he reaches the final stages. Although Mr Duncan Smith has said he is his "own man", his team believes her backingwill help to counterbalance Mr Portillo's higher public profile.
"We fully expect Lady Thatcher's support and, despite what Labour says, she's still phenomenally popular among the rank and file of the party. It's not a question of if, but when, she comes in for us," insisted one Duncan Smith ally.
Her determination to oppose Mr Portillo will have been reinforced by claims in a new book that the shadow Chancellor constantly fought with Mr Hague after joining the shadow Cabinet last year.
At one point, he was said to have demanded Mr Hague denounce Lady Thatcher over her criticism of the idea of a multicultural society.
He is also said to have threatened resignation unless the party ditched its "tax guarantee" scheme to cut tax under all circumstances.
Some Portillo allies would be delighted by a Thatcher endorsement of his closest rival because it would send a powerful public signal that the party had changed fundamentally.
Mr Portillo warned his supporters yesterday that it was "highly dangerous" to vote tactically for Mr Duncan Smith just to stall Mr Clarke. "People might end up being too clever by half and getting a result they don't want," he told BBC2's MetroPol programme.
Mr Duncan Smith said: "If people want me they should vote for me. I don't want anybody voting for me because they don't want somebody else."
Earlier, Mr Clarke told BBC1's Breakfast with Frost the party had not developed enough policy on health, education and transport, the biggest issues facing Britain.
"We didn't even mention them so far as the public were aware during the election campaign. We went on and on about saving the pound."
He added: "I am sorry to upset my colleagues by saying we wasted four years in opposition but if you do get so badly defeated as a party you do have to face up to some painful facts and you have to change."
Writing in The Independent today, Mr Davis calls for a "radical rethink" of how public services operate. He says: "We should move to a system where the state is the guarantor, not necessarily the provider, of the mainstream public services, which would still be free at the point of delivery."