Former Education Secretary Nicky Morgan has told ITV News that she does not think the Prime Minister's plan for a new wave of grammar schools will get through the House of Commons.
ITV News Political Correspondent Paul Brand has tweeted:
David Cameron has told ITV News he has no plans for the future after resigning as an MP.
ITV News Deputy Political Editor Chris Ship tweets:
David Cameron told Theresa May of his decision to stand down as a Tory MP this afternoon
David Cameron says he has no current plans for his future but, as former Prime Minister, can't be full constituency MP for people of Witney
Former prime ministers have found that not only does life go on after living at Number 10, but in some cases it actually gets better.
The most recent men to vacate office have shown it can certainly be very lucrative.
Tony Blair made millions from his autobiography and for eight years represented the US, Russia, the UN and the EU as a Middle East Envoy.
He also reportedly earns £250,000 per speech.
Gordon Brown gets a reported £65,000 as an after-dinner speaker and is the United Nations special envoy for education.
Mr Cameron may remain motivated by the public service ideals that drove him into politics, becoming an advocate for a single issue, which would also serve to repair a political legacy badly damaged by the EU referendum result.
If he wants to make money he can go into business knowing he will no longer have to declare the source of his earnings as all MPs must do.
Mr Cameron will also be expected to pen an autobiography or political memoir on his time in Downing Street or perhaps follow other leading politicians into novel writing.
And, of course, there are world lecture forums or the after-dinner circuit that have proven so popularly profitable with his predecessors.
The Liberal Democrat leader has praised Mr Cameron for forming a coalition government but said his main political legacy would be taking the UK out of Europe to the "huge detriment of future generations".
Tim Farron said that the former prime minister had "demonstrated a capacity to think above and beyond tribal politics" by creating the first post-war coalition government between 2010 and 2015.
He also praised Mr Cameron's qualities of "personal courtesy, humour and thoughtfulness" but said the former leader would be mainly remembered for taking the UK out of the EU in a damaging "gamble".
He has lots of things that he should be proud of but sadly his legacy will be one of accidentally removing us from our closest friends and neighbours in Europe.
He took a politically motivated and short-termist gamble with our country's future, and lost to the huge detriment of future generations. He now leaves the rest of us to pick up the pieces.
Theresa May has said she was "proud " to work in David Cameron's government as she thanked him for his service to the country.
The new prime minister said that the Conservatives had achieved "great things" under her predecessor as he resigned from parliament.
I was proud to serve in David Cameron’s Government – and under his leadership we achieved great things. Not just stabilising the economy, but also making great strides in delivering serious social reform.
His commitment to lead a one nation Government is one that I will continue – and I thank him for everything he has done for the Conservative party and the country.
I wish him and his family well for the future.
Former Prime Minister David Cameron stood down as MP for Witney today with immediate effect.
Mr Cameron said he didn't want to be a distraction for new PM, Maidenhead MP, Theresa May.
Mr Cameron, who left as PM a few months ago, shortly after losing the Brexit vote, said it had been a "great honour" to be the MP for the area.
His announcement was a shock to many in Witney. Here's what they had to say.
ITV News Meridian archive: ITV spoke to David Cameron about the poor turnout at the 2001 General Election.
The Prime Minister, Theresa May, has reacted to former Prime Minister, David Cameron's resignation. In a post, on Facebook, Mrs May says "His commitment to lead a one nation Government is one that I will continue."
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We've been going through the ITV News Meridian archive and have found this footage of David Cameron winning the Oxfordshire seat of Witney back in 2001.
After being elected as MP for Witney in the general election, David Cameron was pegged as a rising star.