Moody's ratings agency said on Friday that Britain's vote to leave the European Union was "credit negative" for Britain's sovereign ratings and for other issuers in the country.

"This outcome heralds a prolonged period of policy uncertainty that will weigh on the UK's economic and financial performance," it said in a statement.

"Heightened uncertainty will likely dent investment flows and confidence, weighing on the UK's growth prospects - a credit negative for the UK sovereign and other UK debt issuers."

Moody's rates the UK one notch below triple-A with a stable outlook.