LONDON (Reuters) - Britain should tweak financial rules after full Brexit to keep London’s financial hub competitive and deepen ties with growth markets in Asia, a think tank said in a study on Monday. Britain accounted for nearly a third of financial activity in the European Union, which it left last January, and will no longer have to comply with its rules after Dec. 31. New Financial said in its study “Beyond Brexit”, supported by Barclays bank, that leaving the EU would be a seismic change and involve significant disruption for the banking and finance industry’s relations with the bloc. Britain is unlikely to get much direct access to the EU financial market but will be a significant “free agent” that can use its expertise in derivatives, trading, fintech and sustainable finance to shape global standards, the study said. Big, strategic decisions will be needed but a moratorium on substantial divergence from EU rules for at least a year would give banks a chance to adjust to the new world, it said. “While the geopolitical backdrop is acutely challenging we think there is an opportunity to develop trade in financial services and closer partnerships with markets like the U.S., Japan, Switzerland, and other smaller markets such as Singapore and Australia,” the study said. Tweaks to bank and insurance capital requirements, taxation and supervision would help London stay competitive globally, the study said. Britain should set up a commission to review the competitiveness of the UK financial sector, the study said. UK regulators have pushed back against calls from lawmakers to be given a formal remit to keep London’s financial competitiveness in mind when writing new rules. The study comes ahead of the anticipated publication of the government’s financial services bill setting out a post-Brexit model for regulating finance and keeping it competitive.