Andy Burnham has asked Health Secretary, Jeremy Hunt, to substantiate his claims that the Labour MP hid hospital failings in a "cover up".
He said he was concerned that disclosure rules had been broken and challenged Mr Hunt to apologise.
– Andy Burnham MP, Shadow Health Secretary
It is impossible to see how you can claim this mounted to a cover-up," he told him in a letter.
I therefore ask you, by the end of today, to provide me with evidence to substantiate your assertion.
If you fail to provide such evidence, I will require a full retraction and public apology. If that is not forthcoming I will consider further action.