BRUSSELS (REUTERS) - The leaders of the European Union's three institutions warned Britain on Friday (Jan 31) that unless it adopts the bloc's standards on the environment, labour, taxation and state aid it cannot expect "the highest quality access to the single market".

"Without being a member, you cannot retain the benefits of membership," they said in an op-ed published by several European media on Friday, ahead of Britain's exit from the EU at midnight in Brussels (2300 GMT).

"Without the free movement of people, there can be no free movement of capital, goods and services," European Council President Charles Michel, European Parliament President David Sassoli and European Commission President Ursula von der Leyen wrote.

The presidents were due to comment on Brexit and the future of the EU at 11am (1000 GMT).

Britain will no longer be an EU member state from Saturday, and will be considered a third country, but it will enter a transition period until the end of December that is meant to give citizens and businesses time to adapt.

The two sides will have 11 months to hammer out an agreement on the shape of their future relationship, negotiating on trade, fishing rights and a raft of other issues.

Although the aim is to achieve a "zero tariff, zero quota" trade deal, the EU says that would also require "zero dumping".

It will insist that Britain remains aligned on standards and regulations to guarantee fair competition, but London has already indicated it will not be "a rule taker".

During the transition period, Britain will continue to apply EU laws but will no longer be represented in EU institutions, and British diplomats in Brussels will have to surrender their passes to the European Council.

EU officials were reminded this week, ahead of Britain's exit, that they should not disclose confidential information about the bloc's business.