Prince William and Kate Middleton were chased in their car

It comes after Prince William and Kate Middleton were allegedly pursued "aggressively" by paparazzi.

Tory MP John Whittingdale said the Press Complaints Commission (PCC) must make it "absolutely clear" that photos should not be obtained by harassment.

London's Evening Standard carried a photo of the couple after a night out.

Prince William and Ms Middleton, who have rekindled their relationship after splitting up briefly in April, were leaving the Boujis nightclub in London during the early hours of Friday morning when the photograph was taken.

Both the Daily Mirror and the Standard's sister paper, the Daily Mail, chose not to use the image.

ABOUT THE PCC It handles complaints from the public about newspapers and magazines The PCC, which is self-regulatory, handled 3,325 complaints in 2006 Every complaint made is then investigated under the editors' code of practice The code was drawn up by editors and covers the way stories are reported Special protection is provided for vulnerable groups, such as children and hospital patients If a newspaper breaches the code, the editor must publish the PCC's criticism in full It cannot instruct newspapers and magazines to withhold publication of an article The current chairman is Sir Christopher Meyer

The incident has prompted the PCC to warn editors against photos obtained by harassment.

In a statement, it said that while freelance photographers were not directly regulated by the organisation, editors must not publish photographs which were taken through harassment.

Mr Whittingdale told BBC Radio Four's Today programme: "The Press Complaints Commission needs to talk to the editors and make it absolutely clear that they should not use any pictures that were taken by means of harassment of the couple.

"That needs to be a generally agreed statement that the press make."

Clarence House officials said the prince was "left concerned" after he and Miss Middleton were "aggressively" pursued.

'Civilised and controlled'

Prince William's spokesman said the events were "incomprehensible" at this time.

This week saw the start of an inquest into the death of William's mother, Diana, Princess of Wales, whose car crashed in Paris in 1997 as she was being followed by photographers.

Alessandro Copetti, who took the picture published in the Evening Standard, defended his conduct, saying the image had been taken "in a civilised and controlled manner".

He said that the prince's car was only followed when it returned to the club shortly after leaving.

It seems incomprehensible, particularly at this time, that this behaviour is still going on Paddy Harverson Prince William's spokesman

Mr Copetti told BBC Radio Five Live: "I took the pictures like I normally do, outside a nightclub when the car was still, stopped outside a nightclub, took them from the front of the window, nobody tried to stop me.

"There were two security guys, one driving, one sitting in front, nobody tried to stop me."

On Friday, Paddy Harverson, the prince's spokesman, said William had been "concerned by the threatening behaviour of the paparazzi".

"Having already been photographed leaving the club, he and Kate Middleton were then pursued in his car by photographers on motorcycles, in vehicles and on foot," said the spokesman.

"The aggressive pursuit was potentially dangerous and worrying for them. It seems incomprehensible, particularly at this time, that this behaviour is still going on."

Diana inquest

The Press Complaints Commission acknowledged that it can "be difficult for editors to establish the exact circumstances in which a photograph is taken.

"But it is of the utmost importance not to use photographs which have been taken in a manner that may have compromised the safety of individuals, which may include pursuit in vehicles."

The prince and Miss Middleton met while at St Andrews University.

The inquest into the deaths of Princess Diana and her companion Dodi Al Fayed began on Tuesday at the High Court.

The jury has heard how several photographers pursued the princess's Mercedes prior to the fatal crash in the Pont de l'Alma tunnel, which killed her, Mr Al Fayed and their driver Henri Paul.