DOWNING Street has played down questions about the mounting speculation as to the identities of the two mystery figures allegedly involved in a secret No 10 love affair.

The internet has been awash with rumours about who they could be.

Asked if David Cameron had concerns there might be security implications because of the alleged affair, his spokesman replied: "I'm conscious there's a lot of speculation around unnamed individuals but I have no further comment to make on that." He denied the PM had held "crisis talks" over the matter.

Mr Cameron was said to have been stunned when he was told the identities of the two supposed lovers and "immediately realised the importance of the story". A source said: "This revelation is dynamite. None of us could believe it when we first heard it, then we just thought – what a complete mess."

The PM and his aides were said to have discussed the potential fallout should the details ever be made public.

The alleged affair, which is believed to have been revealed to the PM during the past few weeks, is also said to have caused "great personal distress to innocent parties". Legal reasons mean no details of the alleged relationship have been disclosed but it has been suggested those reputedly involved are middle-aged and that the affair has now ended.

No current Cabinet member is believed to have been involved but it is said the alleged affair could be as publicly shocking as that between former Tory premier John Major and ex-minister Edwina Currie.

Nonetheless, the mounting speculation might have serious political implications. Because of the absence of details, it is not possible to know if there could be any security or policy implications resulting from the alleged Downing Street affair.