A member of the Queen's staff has been sacked after allegedly making remarks about poisoning her food.

A spokesman for Buckingham Palace said the woman was employed as a probationary kitchen porter. She was dismissed a month ago for making what palace officials described as "inappropriate comments."

She is believed to have said she could poison the Queen with cyanide, and then to have asked other members of staff how she could obtain the chemical.

The woman is said to have been escorted from the Sandringham estate in Norfolk following her dismissal.

It is also claimed in a Sunday newspaper that several days after she was spotted near Buckingham Palace and St James's Palace in central London.

The BBC's Royal correspondent, Nicholas Witchell, says the woman had joined the royal staff in December, and had gone to Sandringham when the Royal Family went there over Christmas and the New Year.

'Alarming'

Mr Witchell told BBC Radio 5 Live: "No further action against the woman is being taken by either the Royal Family or the Royal Protection Squad, and although it was alarming, they do not believe that necessarily this was a serious enough matter to warrant prosecution.

"But it was certainly serious enough to for them to consider that this woman was not an appropriate member of staff, for her to be going around the kitchen talking about even the thought of poison."

Anyone who applies for a job on the royal staff faces vetting by palace officials.

Instability

"All members of staff are subject to security and medical checks to try to ascertain if there is any form of instability in any person's background," said Mr Witchell.

"On this occasion this woman was employed but the palace would say there was no direct threat to the Queen's well being, and the matter was very quickly reported to senior members of staff who dealt with it."

Royal security has been breached on a number of occasions, most famously in 1982 when Michael Fagan broke into the Queen's bedroom at Buckingham Palace.

An escaped psychiatric patient has also managed to get in the grounds, and on another occasion a group of lesbian anti-nuclear demonstrators scaled the walls with ladders.

And last year a report from police gave a warning that more than 6,000 mentally disturbed persons have visited Britain's royal palaces or written persistently to the Royal Family in the past six years.