The Daily Mirror admitted today that it "got it wrong" after publishing a photograph that Kate Middleton, the girlfriend of Prince William, claimed was obtained by harassment.

Richard Wallace, the newspaper's Editor, said today that he and other staff "sincerely regret" having published the image, which shows her walking down the street with a cup of coffee.

The Mirror's statement came after the newspaper became the first ever to be reported by Miss Middleton to the Press Complaints Commission (PCC), Britain's media watchdog, for using the picture.

Prince William's girlfriend claimed that the photographer in question had obtained the shot after harassing her as she walked. The Mirror was the only newspaper that used the image, which was taken by a freelancer.

"On Thursday, we published an innocuous picture of Ms Middleton walking down the street with a cup of coffee," Mr Wallace said today in a statement.

"It was taken by a freelance photographer in circumstances where we were later told she felt harassed.

"We got it wrong and we sincerely regret that."

The PCC, however, confirmed that it was continuing with its investigation, despite the Mirror's statement, until Miss Middleton told them otherwise.

A spokesman said: "As far as the PCC is concerned, we’re still in the process of investigating the complaint. It’s for the complainant to see how she feels about this response."

Miss Middleton's lawyers, Harbottle & Lewis, which made the complaint yesterday, made no immediate comment when contacted this afternoon.

The close-up image published in the Mirror yesterday showed Miss Middleton wearing sunglasses and walking along clutching a cup and her car keys.

The picture is the first used by a British newspaper of Miss Middleton on her way to work since she encountered a media scrum outside her flat on her birthday in January.

At that time, Harbottle & Lewis wrote to the PCC saying they had "disturbing" film of photographers intruding on Miss Middleton's privacy, and the watchdog forwarded the letter to newspaper editors claiming it was a "final warning".

News International - which owns the The Times, Sunday Times, The Sun, the News of the World and the freesheet thelondonpaper - responded to the PCC's appeal by introducing a self-imposed ban on using paparazzi pictures of Miss Middleton, a move welcomed by Clarence House.

Miss Middleton and Prince William, who met at St Andrews University in Scotland where they were flatmates, have been dating for several years.

Speculation that they will one day marry gathered pace in December, when Miss Middleton turned up to watch William graduate from Sandhurst in front of the Queen.

The Prince's concerns over his girlfriend's treatment by the tabloids are particularly poignant as his mother, Diana Princess of Wales, famously died in a car crash in Paris after being pursued late at night by the paparazzi.

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