As Cabinet splits on Iraq deepen, Tory divisions have broken out into the open with the resignation of a frontbench MP.

John Randall, the MP for Uxbridge, wrote to Iain Duncan Smith setting out his decision to resign from the opposition whips office.

Randall, widely seen as a more moderate Tory, said he wanted to have the "freedom of the backbenches" to speak out on Iraq.

Conservative MPs are privately expressing growing unease at the leadership's unbending support for the government.

Whilst Randall is the first MP to resign, several frontbenchers are expressing disquiet.

Thirteen MPs voted against war during a recent Commons motion and a significant number of frontbenchers abstained.

They included shadow ministers Geoffrey Clifton-Brown, James Gray, Jonathan Sayeed and David Wilshire.

Ken Clarke, the former leadership contender, has voiced his alarm at the government's Iraq policy.

Other senior Tories opposed to Duncan Smith's hawkish stance include Peter Ainsworth, John Gummer, John Horam and Edward Leigh.