THE former UK foreign secretary Jack Straw is to face potentially explosive questioning at the Chilcot inquiry into the Iraq war in London next month over a private letter he sent to Tony Blair on the eve of the invasion, urging the prime minister to look at options apart from pressing ahead with British military involvement in the attack.

It is understood the inquiry is to receive a copy of the personal letter sent by Straw — the lord chancellor, with responsibility for the justice system — after discussions with Sir Michael (now Lord) Jay, the UK Foreign Office permanent secretary, on March 16, 2003, two days before the House of Commons voted to back the war.

Straw was named by the Chilcot inquiry as one of its star witnesses next month. Ten serving or former cabinet ministers have been called, including Tony Blair, the former attorney general Lord Goldsmith and the former UK defence secretary Geoff Hoon.

But the inquiry has controversially decided not to cross-examine Gordon Brown before the general election, on the basis that it would be wrong to interrogate any serving minister still holding ministerial responsibility for Iraq. Straw is not exempted on this basis because he is now lord chancellor.

It has been claimed that in the letter Straw suggested the UK should offer the Americans “political and moral support” in their campaign against Saddam Hussein, but not military backing.

He reportedly urged Blair to tell George Bush that British troops would help clear up the mess and keep the peace once the war was over, but could play no part in Saddam's overthrow.

The US president had offered Blair the chance to pull out, and the then chief of the defence staff, Lord Boyce, has told the Chilcot inquiry that the US invasion would not have been delayed by more than a week if British military forces had been held back at the last minute.

The British prime minister's office in Downing Street, London, has never denied the existence of Straw's letter, but claims he did not oppose British involvement in the war, and instead merely set out the options for how the UK could remain involved in Iraq's reconstruction in the event of MPs voting to oppose British military involvement.

— The Guardian, London