A former Conservative Party treasurer has defended leader David Cameron from recent criticism and urged senior members to "show discipline".
Mr Cameron says he is setting a 'clear direction' for the party
Lord Marland of Odstock told the Daily Telegraph that Mr Cameron had hit a "turbulent period" and needed support.
He said he was "surprised" that Conservative donor Sir Tom Cowie had withdrawn his backing last week.
Mr Cameron, who has faced criticism from several prominent Tories, has said he will focus on the "big issues".
Lord Marland said: "It is very unfortunate when people jump on the criticism bandwagon when you hit turbulent times because you are playing straight into the hands of our opposition.
"I would urge all supporters to keep their own counsel and to debate behind closed doors and show discipline.
"David Cameron was elected on a change agenda, a change of emphasis, a change of strategy and a change of direction of the party."
Sir Tom, an entrepreneur who has given the Tories £650,000, last week accused Mr Cameron of being an "arrogant, Old Etonian" style of leadership and said he had become "disillusioned".
He cited the party leader's decision to go to Rwanda during the recent flooding in England, which affected Mr Cameron's Witney constituency, and the row over ending support for grammar schools.
Last month, former Cameron supporter Ali Miraj accused the leader of "box-ticking and gimmickry."
Another former party treasurer, Lord Kalms, has also called for "some rethinking" of policies, while former Tory frontbencher Graham Brady, who stepped down over the recent row about grammar schools, said Mr Cameron was failing to reach out to voters in the north and Midlands.
As Tory critics and supporters continue to debate, Prime Minister Gordon Brown has enjoyed a lead in several recent opinion polls.
But Mr Cameron has said he believed this situation was temporary, adding: "New prime ministers always get a honeymoon and a bounce in the polls."
He added: "If you are leading a political party, if you are setting a clear direction, if you are taking your party and saying: 'Look, we have lost three elections, changes needed to be made, this is the agenda we are going to follow' - of course you face criticism."