By Dhara Ranasinghe

LONDON (Reuters) - The head of bonds at the world's largest asset manager said on Thursday that the Bank of England could hold off easing monetary policy, as a debate swirls around the effectiveness of its measures to protect the economy.

BlackRock's Scott Thiel said that the BoE could pause, based on the strength of recent economic data, a day after Prime Minister Theresa May said there had been bad side-effects from the Bank's emergency measures since the financial crisis.

"On the current data, the BoE could pause its current easing cycle," said Thiel, adding that the BoE had a "tough call" to make on the economy following Brexit.

BlackRock has previously warned that Britain could fall into recession over the coming year after the country voted in June to leave the European Union.

Following the Brexit vote, the BoE in August cut interest rates to a record low and began a new round of bond buying known as quantitative easing (QE).

Asked about May's criticism of the BoE's policy, Thiel said that the side effects of QE will be "with us for a long time" and that the BoE has a "delicate act to balance".

Finance minister Philip Hammond will set out next month how Britain will try to rely less on ultra-low interest rates that have hurt savers and focus more on other ways to boost growth, an adviser to May said on Thursday.

May said this week Britain will trigger the process to leave the EU by the end of March, with investors worried that the government's stance points to a so-called "hard Brexit" that would see it left outside the single market in favor of strict controls on migration.

The British pound fell to its weakest against the U.S. dollar in over three decades on those worries [GBP/].

"The initial stance seems more hard line than we were expecting," said Thiel, adding that he wanted to see how this would "evolve together" with the BOE's recent easing measures.

(Reporting by Dhara Ranasinghe; Writing by John Geddie; Editing by Larry King)