Boris Johnson was dealt a major PR blow when extramarital affairs website Ashley Madison used his image to promote its controversial services.

The website ( promises that affairs are “guaranteed”, especially if you’re married and even if you look like the London mayor!

In a dig at Johnson for his own extramarital dalliances, Ashely Madison has erected a billboard in Camden, north London, showing the mayor’s face next to the tag line, “Affairs guaranteed. Even if you look like this.”

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Infidelity website Ashley Madison launches in UK

Johnson is said to be furious about the advert and will be seeking legal advice.

Ashley Madison, however, are unrepentant, saying: “If you choose public life and to have affairs in public life, then you should have an expectation people will talk about it.”

CEO Noel Biderman said: "The mayor typifies what is all about. He represents the busy, well-off professionals that flock to our site every day."

Johnson is thought to have had three affairs during the time he has been married.

In 2004, he lost his job in the shadow cabinet after lying about his alleged affair with writer Petronella Wyatt.

He went on to cheat on his wife with Times Higher Education Supplement journalist Anna Fazackerley.

Most recently, Johnson allegedly fathered a love child with Helen Macintyre, an art consultant.

The campaign is a piece of marketing genius for Ashley Madison and is likely to generate mass publicity due to the controversial nature of its unwilling poster boy.

In previous ads, Bill Clinton and Arnold Schwarzenegger have seen their faces used to encourage extramarital dating, while Bunga Bunga-ing Silvio Berlusconi will apparently be used in Italian versions of the campaign.

Globally, Ashley Madison claims to have more than11,080,000 members. Under its ‘Affair Guarantee Programme’ the website promises your money back if you haven’t managed to cheat on your partner within three months of signing up.

Tempted? Who knows, Boris Johnson could be waiting for you…