Conservative leader Michael Howard says he is "not bothered" by criticisms of his performance.
Mr Howard has been urged to stay the course
On Monday, Mr Howard said he "very much hoped" to be prime minister after the next general election.
The last two weeks have seen the Tories come third in two by-elections and the government survive the Butler report on pre-war intelligence.
Two ex-ministers have suggested there have been "mutterings" among the Tory ranks about Mr Howard's leadership.
The comments came from former defence secretaries Michael Portillo and Sir Malcolm Rifkind.
Former Conservative chairman Lord Tebbit has denied describing Mr Howard's leadership as "colourless".
He says Mr Howard is capable of winning an election but has "too many dead weights on his front bench to do so".
Asked about the "mutterings" at a Tory policy launch in Westminster, Mr Howard said: "These things always crop up from time to time.
"It's not the first time and I'm sure it will not be the last."
Shadow chancellor Oliver Letwin also mounted a resolute defence of Mr Howard.
"Nobody in the Conservative Party is in the slightest doubt that we have the best leader that the Conservative Party has any chance of having over many years, or has had for many years.
"He is a superb leader, who will lead us into the next general election and to success in it."
Shadow environment secretary Tim Yeo dismissed the "murmurings" about Mr
Howard as "idle chatter".
The Tories were not favourites to win the next election but did have a "good chance", argued Mr Yeo.
"Last summer we were not even in the race," he added.
'Hold your nerve'
Some ex-ministers are urging Mr Howard to resist a lurch to the right, despite Lord Tebbit's advice.
Mr Portillo argued in a Sunday Times article that the Conservative Party could only win from the political centre ground.
His message was echoed by former deputy prime minister Lord Heseltine, who said a move to the right would be a "suicide decision".
The criticisms rose after last week's debate on the Butler report, which saw Mr Howard say he would not have backed the wording of the government motion on the Iraq war, but still backed the conflict.
Tory insiders say Mr Howard would admit the debate was not his best performance but insist morale among party staff was still strong.
The Conservative candidate in last month's London Mayoral election Steven Norris said the party had to "raise its game" if it was to win the general election.
Its key challenge was to "see off the Liberal Democrats", he added.
His comments follow a Populus poll of 1,008 adults for the News of the World which found the Tories and Lib Dems tied in second place on 28% behind Labour on 30%.
"What Michael has done is shown that we have the ideas, we have the plans that will deliver better schools and hospitals for people."