02/06/2013 08:00 BST | Updated 02/06/2013 08:04 BST

Downing Street 'Rocked By Secret Affair'

A general view of the door to 10 Downing Street in Westminster, London.

A "secret love affair" has rocked Downing Street, it has been claimed.

The Mail on Sunday reports that David Cameron has held "crisis talks" after being told of the "sensational affair."

The newspaper says it is unable to disclose any details of the people involved "for legal reasons", but says neither are serving in the Cabinet.

It quotes a source saying: "This revelation is dynamite. None of us could believe it when we first heard it.

"Then we just thought, “What a complete mess”."

Cameron was said to be "stunned" when he heard of the news.

The Prime Minister is already under pressure following a backbench revolt on Europe, and disquiet over the coalition's plans to legalise gay marriage.