Shadow home secretary David Davis's intervention follows uproar in the Conservative Party after David Cameron ruled out a new generation of selective schooling.

The Tory leader has come under intense pressure to disown the suggestion by shadow education secretary David Willetts that grammar schools tend to impede social mobility.

Mr Davis set himself at odds with that view, saying: "My primary interest in this is the simple issue of social mobility - making sure youngsters get the best chances.

"Now, there is more than one way to do that. Grammar schools is one, and where they're there we will continue with them."

Mr Davis, who called for more grammar schools during the 2005 Tory leadership contest, said his support for the leadership's stance was a condition of his Shadow Cabinet membership.

Amid the revolt from grammar schools supporters, Mr Willetts said that where selective schooling already existed, new grammars might be introduced to cope with demand.

The move was portrayed as a U-turn under pressure from party members, following the resignation of Europe spokesman Graham Brady.

In a recent speech, Mr Cameron said the best way to improve social mobility was to ensure "good standards of discipline and behaviour and then good standards of teaching and learning" in all 24,000 state schools, not just the 166 grammar schools.