Former Chancellor Kenneth Clarke says the Ian Duncan Smith's problems are "entirely self-induced".
Mr Clarke and Michael Portillo have publicly denied they are hatching a plot to replace Mr Duncan Smith.
The pair spoke out as rumours circulated in Westminster that the two had agreed a pact, with Mr Clarke prepared to stand for the leadership with Mr Portillo's support.
Mr Clarke says some people are "getting over-excited" about the apparent crisis in the party.
He added: "I have not been plotting with anybody. I have voted. I voted the same way six weeks ago and nobody took any notice. There is the wisdom of not having three-line whips on these subjects in future."
The two men were among eight senior Conservatives who defied party whips to vote in favour of gay and unmarried couples being able to adopt, a move which sparked Mr Duncan Smith's ultimatum to his party.
Mr Portillo told reporters outside his London home: "I am not plotting in any way. I have made it clear on countless occasions that I would not run for leadership in any circumstances and I make that clear again today."
However, interviewed by BBC Scotland, Mr Clarke later claimed Mr Duncan Smith's aides of "a technique of briefing against his colleagues".
He added if there was a crisis over Mr Duncan Smith's leadership it was "entirely self-induced".
He also said talk of plots was "slightly absurd" and "we shouldn't run ourselves in this way".