Kiefer Sutherland has learned that his bizarre headbutting may have some very serious legal consequences.

Police launched an investigation after the 24 star was accused of going all Jack Bauer on designer Jack McCollough at a Met Costume Institute Gala after party on Tuesday night.

Kiefer reportedly took offence after McCollough bumped into actress Brooke Shields at SoHo nightspot SubMercer, although the actress says she is unaware of the reason behind the assault.

The actor is said to have confronted the catwalk mogul and told him to apologise to the star, before headbutting him in the face, injuring his nose.

Now the actor has been told he's to be charged with misdemeanour assault in connection with the incident, and to show up at a New York police station and get a desk appearance ticket for an upcoming arraignment date.

Kiefer - who is well known to enjoy a tipple or ten - is currently under a probation order in Los Angeles relating to his 2007 DUI conviction.

He spent 48 days in jail but could be sent back to prison if he is found to have violated the terms of his release by fighting with McCollough, and his probation is revoked.

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