Pro-leave MPs are preparing to launch a public fightback against a soft Brexit, gathering signatures for a letter insisting Britain must be “well and truly out” of the European Union in March 2019.

Change Britain, the campaign group that evolved out of Vote Leave and has in the past received the backing of the foreign secretary, Boris Johnson, has gathered up to 40 signatures for a letter seen by the BBC and the Times.

Expected to be published in a Sunday newspaper, the letter says: “Continued membership of the single market, even as part of a transitional arrangement, would quite simply mean EU membership by another name – and we cannot allow our country to be kept in the EU by stealth. The government must respect the will of the British people, and that means leaving the single market at the same time as we leave the EU.”

It adds: “The truth is that the single market is a political project, and requires its members to constantly introduce new EU laws. Therefore, the longer one remains a member the harder it is to leave.” It also rejects the idea that the government could continue to pay into the EU budget during any transition period – “pay to play”, as it is known.

The letter is framed as a rejection of Labour policy, which now advocates remaining in the single market and the customs union for the duration of any transition period. That period, according to the policy, should be as long as it takes to negotiate the UK’s future relationship with the EU.

But the row over the details of any transition deal has also been fought out in the cabinet, with Philip Hammond, the chancellor, leading the charge for a prolonged transition to allow businesses time to adjust and prevent a so-called “cliff edge”.

The statement of intent by pro-Brexit MPs will be regarded as an effort to influence debate around the cabinet table, by strengthening the hand of pro-Brexit ministers, including the trade secretary, Liam Fox, who is concerned about his ability to sign new trade deals with non-EU countries.

The MPs also underline one of Fox’s key demands – that the UK be “free to negotiate and sign trade deals during the transition period”.

They add: “Finally, the UK must have the power to take back control of key parts of its immigration system. In short, when we leave in 2019, we need to make sure we are well and truly out.”

The leaked Home Office immigration paper published by the Guardian on Tuesday pointed to firmer controls on freedom of movement immediately on Brexit, raising concerns about whether the EU27 would be willing to negotiate a transition deal that maintained many aspects of the single market, as the government appears to hope.

The letter has been circulating among members of the Conservative backbench European Research Group, chaired by Suella Fernandes, which gathers research and lobbies for Brexit.

Change Britain was co-founded by Dominic Raab, who has since become a junior minister in the Ministry of Justice.

A spokeswoman for Change Britain confirmed that the group had orchestrated the letter, which she said was intended to be supportive of the government’s position and critical of Labour’s call to continue membership of the single market and customs union during the transitional period.

Asked if the letter’s demands on new trade deals, EU budget payments and withdrawal from the transition period were government policy, No 10 said nothing had been agreed.



“We have not negotiated a transition period or what that looks like,” May’s spokeswoman said. “We have said clearly we will leave the single market and the customs union, what happens in the interim period has to be negotiated. We have not even started negotiating that yet.



“We have explained clearly why we want a time-limited implementation period, not going beyond the election. We would like to discuss trade deals in that period but we have to wait to see what happens in the negotiations.”

The letter was being circulated by Fernandes, who is a junior government aide – though she has not signed it herself. Asked whether any minister who signed up would be in breach of their responsibilities, the prime minister’s spokeswoman said: “People have their opinions but I have set out what our intentions are.”



