The Tory front bencher who spoke in defence of grammar schools in The Times yesterday has quit his job.

Graham Brady announced he was resigning his position as Europe Spokesman this afternoon, after overnight briefing to newspapers that he would be sacked by David Cameron at the next reshuffle.

Mr Brady incurred the wrath of the Tory leader after suggesting that selection at 11 raised GCSE standards for everyone in the area, especially ethnic minority children. This came a day after Mr Cameron called critics of his refusal to bring back grammar schools "inverse class warriors".

In a letter to Mr Cameron, he said that he had decided to go because the party was undermining grammar schools such as the one in his constituency.

"Like all Members of Parliament who have grammar schools in their constituencies, I must now help to provide the evidence that those schools need to defend themselves. That is why I have felt duty bound to continue my practice of obtaining and publishing facts which demonstrate that selective local education authorities perform better than comprehensive ones."

He added: "Faced with a choice between a front bench position that I have loved and doing what I believe to be right for my constituents and for many hundreds of thousands of families who are ill-served by state education in this country; there is, in conscience only one decision open to me."

He later told The Times that he resigned now because he would be speaking out again, and "I think it is more honourable to go now."

Mr Cameron appointed the shadow paymaster general Mark Francois to take Mr Brady's place on the front bench.

In a reply to Mr Brady's resignation letter, the Tory leader said he respected his decision to step down but wrote: "Two weeks ago you accepted that we should not continue to debate whether to introduce more grammar schools. The reason for this is to allow us to focus on the real issues in our secondary schools."

He added: "As you know, it has never been our policy to undermine existing grammar schools. As David Willetts and I have both said, they are good schools, and we support them."

Frontbenchers are understood to be deeply unhappy with Mr Cameron’s handling of the affair. Yesterday a party spokeswoman briefed that Mr Brady had been "severely reprimanded" by the chief whip, but newspapers this morning reported that he was to lose his job next month. The failure to take decisive action one way or another has caused some to call into question the judgement of Mr Cameron, who has flown off on holiday.

On Sunday Mr Cameron declared the row to be over, insisting that he wanted to focus instead on academic setting within non-selective schools in the hope of creating "effectively a 'grammar stream' in every subject in every school". But yesterday Mr Brady revived the furore by releasing data to The Times that indicated that in areas with no selective education 42.6 per cent of pupils get five or more GCSEs at grade A*-C including English and maths.

This compared with 46 per cent in partially selective areas and 49.8 per cent in areas where all pupils take the 11-plus.

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