Foreign Secretary Philip Hammond has jumped to the defence of the Foreign Office's new cat, after an MP raised "fears" it could be an EU spy.
Tory Keith Simpson, a member of the Intelligence and Security Committee of Parliament, pressed Mr Hammond on whether Palmerston had been sufficiently checked for bugs by GCHQ chiefs.
He was concerned that the new cat, appointed "chief mouser" at the Foreign Office in Whitehall last month, could be working for the EU Commission.
Mr Hammond offered his "categorical" assurance that Palmerston was "performing" his duties well.
During Foreign Office questions in the Commons, Mr Simpson said: "There is a serious point here. Can I ask you whether Palmerston has been security cleared or not?
"You may recall that the Chancellor's cat Freya had access to the Foreign Office, No 10 Downing Street and it was thought that she might have been got at by a foreign power.
"So can I ask you, has he been positively vetted by the security service and scanned for bugs by GCHQ and can you assure the House and the more paranoid element in the Brexiters of Palmerston's British provenance and that he isn't a long-term mole working for the EU Commission?"
It follows similar theories of espionage that plagued Chancellor George Osborne's wandering cat Freya.
To laughter, Mr Hammond said: "After careful consideration we appointed Palmerston the cat last month as chief mouser to the FCO to complement the work of our contractor and I'm pleased to report to the House that he has settled in perfectly and is performing his services more than satisfactorily."
He added: "He's definitely not a mole.
"I can categorically assure you that Palmerston has been regularly vetted. As for being a sleeper, he is definitely a sleeper - I'm told very often in my office.
"But unlike Freya, who went missing for two years, his attendance record has been 100% and my experts tell me that that pretty much rules out the possibility of him being a Commission employee."
Palmerston is now a social media rival to the Foreign Secretary following the success of his official Twitter account.
Mr Hammond said: "I should also tell the House that while Palmerston has so far only caught three mice, his Twitter account, DiploMog, has attracted 8,158 followers with a rate of growth that implies he will overtake me by the summer recess," he said.
Speaker John Bercow intervened to boast about his own well-performing cat.
He said: "May I congratulate the Foreign Secretary on following my excellent example in Speaker's House where for five years we've had a first-class cat which has done the necessary and of course its name is Order."