Gay couples in a civil partnership should get the same tax benefits as married heterosexuals, the leader of the Conservative Party will announce today.

David Cameron is expected to back marriage for gay and straight couples at the National Family and Parenting Institute tomorrow, as well as promising equal “marriage” taxes for gay and lesbian couples.

Mr Cameron is rumoured to say in a speech, “I don’t believe that politicians can take a cold and amoral attitude to family life.

“We can’t just take a vow of silence on the grounds that family life is beyond the reach of hard-edged economics and hard-edged administration.

“But neither do I believe that politicians should be using the levers of power to force people into certain lifestyles or family forms. We must not imagine that legislation, regulation, targets and bureaucracies will somehow be able to engineer happy families.”

The move is expected to rile the more traditional members of the Party.