Former prime minister Tony Abbott appears to have backflipped on his opposition to Britain's exit from the European Union, telling a London audience he was "quietly thrilled" Brexit had succeeded.

Mr Abbott broke with conservative eurosceptic ranks to support Remain prior to the poll. "Britain's challenge now is to save Europe, not leave it," he wrote in a piece for Rupert Murdoch's The Times.

But in a speech delivered at a high-powered business breakfast on Monday, the former PM changed his tune, conceding a latent desire to see his country of birth leave the union.

"First a confession: I was one of the many luminaries to warn Britons against Brexit. Unlike most of them, though, my argument was not that Britain needed Europe but that Europe needed Britain," he began.