Theresa May’s Brexit plan is “profoundly undemocratic” and would lock the UK into the EU’s rules, the leader of the influential European Research Group of Tories has said as he urged colleagues to reject the blueprint.

In a letter to colleagues, Jacob Rees-Mogg said the deal would see the UK hand over £39 billion to the European Union for “little or nothing in return”.

Arch-Brexiteer Mr Rees-Mogg also said the deal was unacceptable to unionists because of its treatment of Northern Ireland and broke Tory manifesto commitments.

In a call for revolt on the Tory benches, he said: “For these reasons I can not support the proposed agreement in Parliament and would hope that Conservative MPs would do likewise.”

He wrote: “The proposed agreement will see the UK hand over £39 billion to the EU for little or nothing in return. The prospect of an agreed free trade agreement is as far away today as it always has been.”

The 15-page political declaration on the future relationship was “neither binding nor clear” and “if it aims to put in place the Chequers proposal it is neither workable nor respectful of the referendum result”.

In an echo of the argument on the Vote Leave bus, Mr Rees-Mogg said: “In the absence of a trade agreement we should spend our money on our own priorities, for instance £39 billion could pay for 26,000 nurses for 40 years.”

Mr Rees-Mogg warned: “This agreement will lock us into an EU customs union and EU laws. This will prevent us pursuing a UK trade policy based around our priorities and economy.

“Without the ability to regulate our own economy and form our own trade agreements we will lose out on the opportunities that Brexit affords us.”

Agreeing to the rules of the customs union “in contravention of the 2017 Conservative manifesto, without any votes or influence, is profoundly undemocratic”.

“This is compounded by the lack of any ability for the UK to unilaterally escape, making the UK a permanent rule taker,” he added.

He said the proposals would treat Northern Ireland differently from the rest of the UK, which was unacceptable to unionists in both Northern Ireland and Scotland.

The letter comes a day after Mr Rees-Mogg suggested his patience with Mrs May was running out.

Mr Rees-Mogg, who has previously held back from calling for Mrs May’s removal, said on Tuesday that “there comes a point at which the policy and the individual become so intimately connected that it will be very hard to carry on supporting the person who is promoting this policy”.