Lord Hurd, the former Foreign Secretary, has called on Iain Duncan Smith to make peace with the Tory big guns firing at him from the sidelines.
He cast doubt on whether the Conservatives could win the next election and demanded a shake-up in the rules for choosing party leaders.
His wide-ranging criticism of the state of the party comes days before the Conservative conference, which starts in Blackpool on Monday.
Party chiefs plan to use the conference as a springboard to capitalise on the Government's woes. A series of new policies, focusing on the theme of trust, will be launched over the coming week by shadow Ministers.
But Lord Hurd, in a GMTV interview to be broadcast tomorrow, gave a gloomy prognosis of the party's prospects. He contrasted Tony Blair, who he said had lost much of his public trust, with plain-speaking Iain Duncan Smith. "He doesn't pretend to be anything else, so we have a chance on that ground, but there is still a lot to do. The party is still on the runway."
Lord Hurd said he had urged the Tory leader to bring senior former ministers in from the cold. "I think he needs to get in touch with, and make a compact with, the big boys who are not in the shadow Cabinet."
He named Kenneth Clarke, Michael Heseltine and Michael Portillo, who were well-known and had "a reputation and some strength". Lord Hurd said: "It's not good to have them on the sidelines every now and then saying something that is not helpful.
"Of course they won't agree on everything, but there are certain things they will all say the Tory party stands for - they need to work that out."
Lord Hurd said he thought victory at the next election was possible, but said there was "some truth" in the view that the Conservatives should concentrate on the election after next.
In what will be viewed as a swipe at the system that secured Mr Duncan Smith's selection as leader, Lord Hurd called for the final say on who leads them to be returned to MPs. He said: "They're actually going to be in the best position to make a choice."
He spoke out as backbenchers privately expressed fears over the party's failure to make better progress in the polls. One MP said: "The situation is a very shaming indictment of the official opposition. It's all a bloody shambles."
Meanwhile Michael Ancram, the shadow Foreign Secretary, pledged yesterday that the party would run a national campaign to press the Government to hold a referendum on the new EU constitution. He told the BBC: "The Government has copped out on this ... They are just going to go through the motions.
"It is our job now to explain, hopefully not only to the people of this country but also to other countries of Europe, the dangers of the route that is being taken with this constitution.
"We are going to have to mount a major campaign to make the Government change its mind about a referendum. It is quite extraordinary that Spain is going to have a referendum, Ireland is going to have a referendum, Denmark is going to have a referendum, possibly France is going to have a referendum. Yet the British people, according to this Government, are not allowed to choose."