Iain Duncan Smith pushed his party to the very edge last night by delivering an ultimatum that left his position as Tory leader in great danger.

His dramatic statement that the party must "unite or die" behind him was met with a mixture of anger and disdain.

Last night, his attempt to quash the rebellion, which started on Monday night when eight leading Tories voted against his policy on adoption rights for unmarried and gay couples and another 35 mysteriously absented themselves from the House, appeared to have backfired.

In a dramatic day, Mr Duncan Smith cancelled a scheduled policy initiative to make a "personal statement" at Tory headquarters.

He said: "A small group of my parliamentary colleagues have decided consciously to undermine my leadership.

"For a few, last night's vote was not about adoption, but an attempt to challenge my mandate to lead this party. We cannot go on in this fashion. We have to pull together, or we will hang apart.

"My message is simple and stark: unite or die."

Michael Portillo, one of the big names who voted against the party line, protested his loyalty to the party leadership but accused Mr Duncan Smith of an "unwarranted mis-interpretation" of MPs' motives.

He said: "I voted against a three-line whip for the first time in my life because I believed it was wrong and inconsistent to use coercion on adoption, and that was my only reason for doing so."

Rebel Kenneth Clarke, the former Chancellor of the Exchequer who still harbours leadership ambitions of his own, said: "It would be much easier to unite as a party if Iain Duncan Smith would refrain from imposing three-line whips on subjects which have always been left to the judgement of individual MPs."

David Curry, MP for Skipton and Ripon, was one of the rebels, as was Totnes MP Anthony Steen who was scathing about Mr Duncan Smith.

"I have come to the conclusion he is murally dyslexic. It means he doesn't see the writing on the wall," he said.

"He would see this message - that the party and the MPs desperately want him to succeed - but everything he is doing is actually making that not possible.

"When he said in his statement there was a small minority, he was referring to a quarter of the parliamentary party.

"He also accused those people of being disloyal, but what did he think he was doing when he voted against his own (John) Major Government 50 times?"

Francis Maude, who also voted against the Tory whip, said Mr Duncan Smith had chosen the wrong ground on which to fight.

"It was an issue not of overwhelming importance. This is not an issue people wake up in the morning worrying about."

Conservative Central Office released a series of emails from constituency chairmen which showed grassroots support for Mr Duncan Smith and which attacked the "disgraceful behaviour" of the "failed ex-ministers" who voted against him.

However, Rod Reed, chairman of Beckenham Conservative Association in Kent, said: "Morale is at rock bottom and a lot of people are saying quietly they are dissatisfied."

* The Lords last night bowed to the Commons and backed the plans to allow unmarried couples, including gays, to adopt. Voting was 215 to 184. Peers last month rejected the move but were asked to reconsider when MPs on Monday overturned that vote.