Sir John Chilcot will refuse to reveal if he thinks Tony Blair broke the law over Iraq when he appears before MPs this week, according to well-placed sources.

Answering questions for the first time since his report was published, Sir John is expected to say commenting on the legality of the invasion is outside his remit.

He will also rebut attempts from MPs to reveal if Mr Blair and other leading Labour politicians watered down key criticisms in his report, sources said.

The stance is likely to infuriate the families of soldiers killed in Iraq, who have commissioned lawyers to look into whether Mr Blair could be sued for his decisions.