A Conservative minister in the 1960s sold information about his colleagues and Parliament to communist spies, it has emerged.
Czech Security Service files reveal Raymond Mawby, who died in 1990, was in its pay for a decade, according to the BBC.
He supplied spies with a floorplan of the prime minister's Commons office, lists of parliamentary committees, information about colleagues and a supposedly confidential parliamentary investigation into a Conservative peer, it found.
Mawby, who served as MP for Totnes from 1955 until he was deselected in 1983, was a gambler and began accepting "loans" while playing roulette and other games, the files show.
He later went on to accept payments, usually for £100 a time, for information and was given the codename Laval.
"Mawby has also promised to carry out tasks such as asking questions in Parliament according to our needs," documents written by a Czech handler in 1962 show.
Czech spies noted "His leisure time he spends in bars… and also loves gambling.
"While playing roulette and other games he is willing to accept a monetary 'loan' which was exploited twice."
Mawby became assistant postmaster general and a junior minister in 1963.
His handler feared the promotion could end their arrangement as it meant a salary increase of £2,000 a year, but the MP continued the arrangement.
As well as supplying information about the layout of the PM's parliamentary office, he provided details about its security arrangements.
"I recommend giving Laval at the following meeting before Christmas £100 on the understanding that he will provide us with the requested plan," the handler wrote.
The BBC said the file showed the relationship ending in November 1971.