Theresa May has been told by Conservative Eurosceptics that they will not accept a long period in which Britain must stick to EU rules

Britain will ask the European Union to extend the Brexit transition period beyond 2020 with a “duration determined by how long it will take to prepare and implement the future partnership”.

Government sources have admitted that the request for more time comes as cabinet divisions delay a decision on Britain’s future relationship with the EU.

The extension will anger Conservative Eurosceptics who have described the transition as reducing Britain to a “vassal state”.

A draft government negotiating document seen by The Times nudges the government into a transition lasting longer than the current proposal of 21 months after Brexit on March 29, 2019, during which time Britain will have to abide by all EU rules, including free movement, without any say in decisions.

“The UK