Tony Blair went to the opera in St Petersburg with Vladimir Putin in 2000, only weeks before the Russian presidential election that cemented his grip on power

MI6’s assistance to Vladimir Putin during his rise to power, whereby it ensured that Tony Blair attended a social event with him, is now regretted, its former head has admitted.

Sir Richard Dearlove, who was chief of the Secret Intelligence Service from 1999 to 2004, said that in the run-up to the Russian presidential election in 2000 he had been approached by a senior KGB officer in London asking for MI6’s help.

The officer asked if Mr Blair, when he was prime minister, would be willing to attend the premiere of Sergei Prokofiev’s War and Peace opera at the Mariinsky Theatre in St Petersburg alongside Mr Putin.

“We had a long discussion in London whether Tony Blair should accept the invitation or not and we