I'll wager that there's a law on the books in Britain that protects a government official from any such action....just as our Congresscritters cannot be sued for *anything* they say on the floor of the House/Senate about *anyone*.
There is a law of immunity from slander/libel for anything they say whilst in the House of Commons. In fact a common defence against scurrilous allegations made there is to challenge the asserter to say them outside the house, where parliamentary privilige does not count.