The shadow culture secretary told the party conference in Blackpool that grabbing headlines had not worked over the last eight years.

"From now on, we will have to be scrupulously honest and painfully reasonable," she said.

But she gave no clue about whether she intends to join the leadership race.

'No easy answers'

Mrs May said Labour knew nobody trusted it but also knew nobody trusted the Tories either.

There had to be a change in the style of opposition to regain respect, she argued.

"We'll have to stop opposing for opposition's sake - and resist all temptation to be opportunistic," she said.

Other vices the party had to give up include intellectual self-indulgence, ideological obsessions, quick fixes and easy answers.

Equality warning

Mrs May caused a stir in 2002 when she said the Conservatives were still seen as the "nasty party".

On Monday she said the party must be representative of men and women of every age, race and religion.

She said: "For the small minority who don't accept women - or black or gay people - as their equals, I've got a message.

"Don't think you'll find a refuge from the modern world here. There is no place for you in our Conservative Party.

"Because every day that we are unwilling to embrace a future in which all men and women respect each other as absolute equals is another day we will be out of government."

Mrs May, who says she has been considering standing in the contest to replace Michael Howard, was the first of the possible contenders to address the conference.

She was followed by Sir Malcolm Rifkind, who is one of the five leadership contenders to declare so far. The others are David Davis, Kenneth Clarke, David Cameron and Liam Fox.