It may have been accidental that a bugging device concealed in a prison table picked up an MP's conversation. But the Sadiq Khan affair has stirred debate over whether politicians ought to remain exempt from the wire-tap surveillance.

In 1966 Harold Wilson made bugging MPs illegal. That a paranoid group within MI5 believed the Labour Prime Minister was a KGB spy gave him good reason to question the security service's intrusions into politicians' privacy.

But the Prime Minister was mistaken in assuming that the spooks did not have grounds for wanting to monitor some of his parliamentary colleagues.

In 1969 Joseph Frolik, an officer in StB, the Czech intelligence service, defected to the West. Interrogated, he named several Labour MPs as being on the Czech spy payroll. They included John Stonehouse, Tom Driberg, Will Owen and Barnett Stross.

Defectors sometimes elaborate stories in order to be more highly prized. This may well have been the case with Frolik. However, at the height of the Cold War, MI5 would surely have been derogating its duty not to investigate his claims. Indeed, several of those MPs he named were, or had been, in the pay of foreign powers.

Despite being acquitted at his trial in 1970, Will Owen had for years taken £500 a month from his Czech handlers in return for giving them the deliberations of the Commons Defence Estimates Committee on which he sat. True, a subscription to something like Jane's Defence Weekly might have cost less and been of comparable value, but the MP for Morpeth had compromised himself nonetheless. The same can be said of Barnett Stross, known to his handlers as Agent Gustav.

The revelations from the Mitrokhin Archive confirm that the KGB had compromised the Labour Party chairman, Tom Driberg. Admittedly, a man more easy to compromise it would be hard to find. Indeed the compulsive “cottager” and gossiper, given the suitably camp codename Agent Lepage, also found time to assist the Czechs and MI5 with their inquiries.

Meanwhile, MI5 wanted to investigate Frolik's claims that, as Aviation Minister, John Stonehouse had passed Concorde's technical secrets to the Russians. Wilson refused permission to have Stonehouse bugged, preferring only to allow a light questioning of the minister in Wilson's presence.

Given Stonehouse's subsequent antics, including fraud, faked suicide and a secret life in Australia, it might have been better keeping tabs on his movements. As we now know, he was in the Czechs' pay.

There may be less good grounds for bugging politicians these days. It would be sad if only Mohamed Al Fayed believed that honourable members were worth bribing.

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