Multi-millionaire art collector Charles Saatchi has boasted about his cage-fighting abilities in a letter to a gossip columnist who called him a coward for the way he treated his ex-wife TV cook Nigella Lawson.

Mr Saatchi, whose marriage to Ms Lawson fell apart after he was pictured with his hand on her throat in a central London restaurant, wrote to The Spectator after its columnist Taki said that "expecting a pornographer to have a heart is like counting upon Charles Saatchi to act like a gentleman".

Writing in his column on January 18, Taki said Saatchi had a "coward's bullying manner" prompting Saatchi's reply which was published today.

In a letter published by the magazine, Saatchi said it was "hapless of you to spring to Nigella's defence last week, as she always found you toe-curlingly vile, and would have been aghast at having you as her valiant supporter".

He went on: "People tell me that in your unreadable column you also like to brag that you are a Black Belt at karate. Well, me too, old boy. But apparently your 'fights' are genteel affairs, against other soppy geriatrics rolling around the floor in crisp white outfits, in some bit of judokai nonsense.

"Mine take place in cages, 20 feet square, unofficial little events with no gloves, no rules, and the loser being carried out, usually battered to bits. You will understand why I laughed out loud at your schoolyard boast that I should try throttling a real hard case like you."

The magazine quoted its columnist as saying he was "willing to face" Saatchi "any time under cage-fighting non-rules" and said it would be "happy" to stage the fight in its garden with proceeds from ticket sales going to the Boxing Academy in East London.