LONDON: Britain will reopen its temporary market access regime for European Union financial firms in September to tide companies over during London's parting of ways with the bloc, the Financial Conduct Authority said on Wednesday.

Britain left the EU in January and a transition period ends in December. It has a "temporary permissions regime", or TPR, to allow EU-based firms to continue serving customers in Britain for a limited period after that so they have time to obtain authorisation under Britain's rules.

The TPR has been closed to new applications, but since then Britain has made it clear it will not apply for an extension to the transition period. "Over 1,000 firms and over 600 fund managers have already notified us, and we will reopen the notification window on 30 September," Nausicaa Delfas, the Financial Conduct Authority's executive director for international, told a City & Financial online event.

"In short, my message to you is that we all need to continue to prepare for a range of scenarios, to be ready for the end of the year," Delfas said.

Britain and the EU have missed an end of June deadline to complete "equivalence" assessments of each other's rules to allow selective access to their respective financial markets. Each blames the other.

Antony Manchester, managing director at BlackRock, said Britain should unilaterally be open to EU financial firms in any case to help London remain a "match-fit" global financial centre that competes with New York and Singapore.

"There will be equivalence ultimately, and that is probably because the EU needs it," Manchester said, adding this would be the case for clearing euro-denominated derivatives in London in the autumn.

Delfas said allowing equivalence-based access was the best way to avoid clashes in derivatives and share trading after December. The EU is concerned that Britain will seek a competitive advantage by easing rules inherited from the bloc. Delfas said Britain supported open markets and high regulatory standards.