Keith Richards said that the unexpected EU referendum result would not lead to major changes in the short term.
The FCA quickly issued a statement on the day the outcome was known to stress that firms must remain compliant with EU regulations because the UK will remain a member until an exit plan has been configured and seen through.
Mr Richards said: “For anyone expecting radical change to the country's regulatory landscape in the wake of last week's decision however, this is unlikely to materialise. The UK has driven its own regulatory agenda for years and has always had the opportunity to apply for variations to EU rules where it feels appropriate.
“The unpredictable or adverse impact however, which may include a restriction on UK advisers being able to operate cross-border, is likely to become clear quite quickly as the EU looks to push the agenda.”
Mr Richards, writing in his PFS blog, said: “Firms covered by MiFID are authorised and regulated in their 'home state' - broadly, the country in which they have their registered office. Once a firm has been authorised, it is able to use the MiFID passport to provide services to clients in other EU member states.
“As a result of Brexit, some UK advisers who provide cross-border advice may have little option but to apply for individual authorisation in different EU states or become a member of an organisation with its registered office in an EU member state such as Ireland.
“Meanwhile, implementation of MiFID II is due by January 2018 - prior to a formal exit from the EU - and the UK's adoption of this wide-ranging legislation will be largely unaffected.
“As negotiations regarding the terms and conditions of the UK's withdrawal from the European Union continue, a degree of uncertainty is likely to linger for some time yet.”
He added: “For professional advisers, this means an increased level of demand from consumers worried about the impact of a future deal on their personal financial circumstances and it has been apparent that many firms have been kept extra busy since the vote was announced.”