When Raymond Mawby went on the BBC’s Late Night Line-Up talk show in 1967 to debate whether homosexuality should be legalised he came across as a quintessential traditional Tory right winger.

“It looks as if I’m the odd man out,” he said. “I think this is dealing with a twilight area of abnormal people and it’s something that should not be open for public discussion.”

As the Conservative MP for Totnes for nearly three decades, Mawby was a dyed in the wool Tory. But in many ways he really was the odd man out. Even as he railed against socially progressive causes he was in fact selling out his country to a foreign power.

New papers unearthed in Prague have revealed that the working-class born politician spied for the Czech secret services providing them with reams of sensitive political information including a hand drawn floor plan of the prime minister’s office.

The new revelations, uncovered by the BBC in the dusty archives of the Czech Security Services, shine a new spotlight on how Communist spy agencies looked to recruit British parliamentarians. It has long been known that the Czechs had proven themselves adept at turning Labour politicians, who were politically closer aligned to them. But this is the first time proof has been unearthed of Prague successfully turning a Conservative politician.

According to the files, Czech spies approached Mawby in November 1960 at a cocktail party and persuaded him to begin supplying political gossip on a regular basis for cash payments. He was known to be a gambler and the spies hoped they could exploit that particular weakness. “His leisure time he spends in bars…and also loves gambling,” an anonymous handler writes at one point in the case notes. “While playing roulette and other games he is willing to accept a monetary ‘loan’ which was exploited twice.”

To begin with the Czechs played Mawby cautiously, asking him for relatively unhelpful gossip on trade unions before requesting that he start supplying more sensitive information. Each time he handed over details he was paid £100 – a handsome regular income on the side at a time when the annual MP’s salary was around £3,200.

“Mawby has also promised to carry out tasks such as asking questions in Parliament according to our needs,” one Czech handler wrote in a plan on how to use him in 1962.

The relationship had become so lucrative for Prague that their spies began to worry when Mawby was promoted to become a junior minister in 1963. The new job meant an extra £2,000 to his salary and his handlers feared he would no longer need the spare cash they gave him for spying. Nonetheless Mawby continued to supply data. Following a meeting in November 1965 Mawby handed over a piece of paper with the names of three new officials on the Conservative Party. His handlers asked him for more information, including a floor plan of the Prime Minister’s office at Number Ten.

“Laval fulfilled this task before our next meeting,” the Czech spy wrote, referring to Mawby’s code name.

The sketch which accompanies the spy’s note is crudely drawn showing doorways, desks and corridors surrounding the PM’s offices. The BBc speculated that it might have proved useful for any spy agency hoping to install bugs or wires in the office.

Mawby’s relationship with the Czech spy service appeared to continue up untikl November 1971 when his file as closed. Two months earlier Britain expelled more than 100 Soviet diplomats from London on a clampdown on Russia intelligence assets.