Iain Duncan Smith has said plots against him have left his party "staring into the abyss".
Duncan Smith insists he will fight the next general election
The Tory leader promised to
fight to stay in his job despite mounting pressure to resign.
A leadership contest would plunge the party into chaos and destroy its chances of winning the next general election, Mr Duncan Smith added.
He told the Mail on Sunday the party was being held to ransom by a "small number of malcontents".
As Tory MPs talk to party workers and activists in their constituencies about his future, their leader said if they lacked the courage or honour to "come out of the
shadows" and challenge him openly, they could not hope to have the character
to run the country.
And he would not be responsible for plunging the party into another
divisive contest, he told the paper.
"If it takes that leap I have to tell it - as its leader - the outcome will be very grave."
Mr Duncan Smith added he was "pressing on" and would set out "our plans for the first Conservative government of the 21st
century" in a speech to the Centre for Policy Studies on Thursday.
The bookies' favourite to take over the leadership, shadow chancellor Michael Howard, told the Sunday Times: "We are on course to present a clear and coherent
programme for government at the next election.
"These are Iain's policies. They
are a tribute to Iain's work.
"Iain has earned the right to carry that work forward.
John Major also told Tory "plotters" to stop damaging the party by undermining their leader.
The former prime minister said the party, and its hundreds of thousands of grassroots activists, did not deserve the speculation surrounding it.
He attacked MPs who were "using the media by briefing them in private" while "proclaiming loyalty" to Mr Duncan Smith in public.
"Everyone should look at the damage that is being caused to the party by what is happening at the moment," Mr Major told BBC Radio 4's Today programme.
"The public absolutely loathes it."
On Friday Tory whips took the rare step of issuing a statement stressing their "total loyalty" to the leader.
Reports Mr Duncan Smith had lost their confidence were outrageous and wrong, the statement said.
Tory chief whip David Maclean said: "I have spoken personally to all the whips and they are unanimous in their support for the leader of the party."