Buckingham Palace said today it was investigating a report that undercover journalists were able to enter the Queen's London residence and sit in her car after bribing a royal chauffeur.
The Royal chauffeur Brian Sirjusingh has been suspended pending an investigation.
The tabloid News of The World said two of its reporters posing as Middle East businessmen paid £1,000 to the chauffeur to evade security checks at the palace.
The paper said the story exposed lax security at the palace. "We could have been al-Qaeda, we could have had a bomb or at least a tracking device," it said.
It said the chauffeur took them to a garage storing Bentley and Rolls-Royce limousines used by the royal family and even let a reporter sit in one of the vehicles.
A palace spokesman said officials would study what had happened. "Any security matter is taken very seriously and we will look into these allegations," she said.
Police said they would discuss the matter with royal staff. "We are naturally concerned about the issues raised by this story and are liaising with palace officials about their staff security arrangements," a Scotland Yard spokeswoman said.
Royal residences have suffered a number of high-profile security breaches in recent years, prompting the appointment of a security supremo after Daily Mirror reporter Ryan Parry spent two months in 2003 working undercover at Buckingham Palace.
He was employed as a footman, walking the queen's corgi dogs and serving her drinks, despite having applied for the job with a false reference.
An official security report following that incident concluded that the most likely threats came from the press or individuals trying to test security measures. But it warned that weaknesses could also be exploited by terrorists.
Earlier the same year Aaron Barschak had evaded security at Windsor Castle west of London wearing a pink dress and an Osama bin Laden-styled beard to gatecrash the 21st birthday party of Prince William, second-in-line for the throne.
In 1982 unemployed labourer Michael Fagan scaled a Buckingham Palace drainpipe to enter the queen's bedroom. He sat chatting with her for 10 minutes before she was able to summon help.