The leaders of Germany, France and Italy have agreed there can be no informal negotiations on Britain leaving the European Union before London triggers the formal application process to leave the bloc, German Chancellor Angela Merkel says.

Britain could have a new prime minister by early September, the Conservative Party says. Graham Brady, chair of the "1922 committee" of Conservative MPs, said the group had recommended the leadership contest begin next week and conclude no later than September 2.

Asked about the possibility of a second EU referendum, Prime Minister David Cameron said the result of last week's vote must be accepted. He confirmed the UK will not trigger formal EU exit talks at this stage.


Ratings agency Standard & Poor's is stripping Britain of its last remaining top-notch credit rating, slashing it from AAA to AA and warning more downgrades could follow.

Britain's Work and Pensions Secretary Stephen Crabb is considering a bid to succeed Cameron, Sky News reports. Former London Mayor Boris Johnson is currently the favourite to replace Cameron.

- Reuters, AAP