THE Tory Party drive to stop Boris Johnson becoming its next leader - Operation Arse - has been hailed a “great success”.

A senior Conservative source, who was one of the instigators of the anti-Johnson strategy, said since the operation was announced at last year’s Tory conference in Birmingham, the former Foreign Secretary’s chances of succeeding Theresa May as leader had fallen away.

The insider, who is close to the Prime Minister, said of Operation Arse: “It seems to me that it was a great success. But should it ever need to be reactivated, it certainly can be.”

He went on: "Boris missed his chance. He's been gone [out of government] for what, six months now? And what's he done? What has he achieved?

"I wouldn't be able to tell you who the front-runner is but it isn't Boris," he added.

The senior source also suggested that the non-appearance of Mr Johnson in Scotland during the entire two-year independence campaign had been deliberate; that the Old Etonian Tory was regarded as a vote loser and not a vote winner for the pro-Union No campaign.

Operation Arse was launched last October at the party conference in Birmingham after internal polling suggested a Johnson premiership would wipe out the Tory gains in Scotland made under the leadership of Ruth Davidson.

A senior party insider said at the time: “We called it that so we’d all be clear who we were talking about.”

The anti-Johnson faction within the Tory Party is thought to include not only Ms Davidson but also her colleague David Mundell, the Scottish Secretary.

Another member Chancellor Philip Hammond, last year suggested Mr Johnson could not do “grown-up politics”, had “no grasp of detail” and that the former mayor of London’s greatest achievement was introducing “Boris bikes” to the capital.

However, one of Mr Johnson’s supporters is Ross Thomson, the embattled pro-Brexit MP for Aberdeen South, who was often seen by Mr Johnson’s side during the autumn party conference.

After the headlines about Operation Arse were published, Mr Thomson took to Twitter to lash out at his colleague’s critics following Mr Johnson’s well-attended set-piece speech at the conference fringe.

He said: “Regardless of your view of @BorisJohnson, today he injected some much-needed energy, optimism, passion and enthusiasm to a flat conference. The reaction in the hall was electric which even those ‘Operation Arsehole’s’ [sic] can’t deny.”