Tory leader David Cameron has called on his party to be "a committed, united and positive opposition".
David Cameron said: 'Now is the time to reaffirm our strategy'
Addressing the backbench 1922 Committee ahead of the parliamentary summer holiday, Mr Cameron said his party could defeat "this tired government".
The Tories have seen rows over grammar schools, an apparent "bounce" in the polls for new PM Gordon Brown and they came third in two recent by-elections.
Tory frontbencher David Davis has also called for "a bit of discipline".
Mr Cameron, in a 15-minute talk on Wednesday, said: "Disunity can undermine our hard work.
"We are a broad church, it should be possible to have a debate and even an argument without it appearing in the papers."
He emphasised that he was committed to his plan: "Now is not time to change our strategy, now is the time to reaffirm our strategy.
"Remember that elections are always won on the centre ground."
Mr Davis, the shadow home secretary admitted the party was going through "a slight difficult phase" but said Mr Cameron had "passed his first test".
Lord Kalms, who supported Mr Davis's own bid for the Tory leadership in 2005, told the BBC on Tuesday: "I'm certainly willing to give him [David Cameron] 100% support and hope he will lead the party in the next election.
"But, nevertheless, between now and then, a lot more work has got to be done, particularly to reassure us that he has policies which are satisfactory to the Conservative Party, the traditional Conservative Party, and to the electorate in general.
"I'm just sending warning signals from the fodder at the back ranks: 'Look, chum, we need to do some rethinking'."
Asked whether he associated himself with those remarks, Mr Davis replied: "No".
He added: "I think the real truth is we are going through a slight difficult phase when we have the 'Brown bounce'.
"My argument to my own party is that David Cameron has passed his first test, it's now time to show a bit of discipline and pass yours."
On Sunday Mr Cameron said he wished the party had done better in recent by-elections in Sedgefield and Ealing Southall, but now it was "on to the next test".
He said there would be "no return to the comfort zone" and he would continue his reforms to move the party "back to the centre ground".
He has also dismissed reports that at least two unnamed Tory MPs were calling for a vote of no confidence in his leadership and has defended his decision to go to Rwanda, while parts of England are badly flooded.