A British picture agency has apologised to Prince William's girlfriend Kate Middleton and agreed to pay compensation for invading her privacy, it said.

A photographer not employed by Rex Features took pictures of Ms Middleton during a holiday with her family at Christmas, the agency said in a statement on its website.

However, the agency syndicated some of the photographs for publication in the foreign media and they appeared in German publications.

Ms Middleton, 28, who was represented by Queen Elizabeth II's lawyers Harbottle and Lewis, was awarded £5,000 in damages, according to The Daily Telegraph newspaper.

"Although at the time Rex Features did not know that an infringement of privacy had occurred, we now accept that this was the case and that by distributing the photographs we were a party to that invasion of privacy.

"Accordingly we have agreed to pay compensation to Ms Middleton and have undertaken not to syndicate any further private photographs of her," said the Rex statement.

"We apologise to Ms Middleton for what has taken place."

There has been growing media speculation that Prince William and Ms Middleton could announce their engagement. The queen's lawyers warned newspapers not to publish paparazzi pictures of the royal family, ahead of their Christmas break.

Prince William, second in line to the throne, voiced concern in 2007 after MS Middleton was hounded by paparazzi outside her London home.

A spokesman for Ms Middleton said she intends to donate the damages to charity.