Theresa May must ask the European Union for a transitional arrangement to avoid a “cliff edge” when Britain leaves the European Union, and offer parliament a vote on the final deal, a powerful committee of MPs from both sides of the Brexit debate has demanded.

As the prime minister prepares to set out her approach in a keynote speech on Tuesday, the first report from the cross-party select committee on Brexit, chaired by Labour’s Hilary Benn, says a transitional deal is essential to prevent economic disruption as Britain leaves.

Its other recommendations include:

The government should publish its Brexit plan by the middle of February, in the form of a white paper rather than the more limited briefing document Conservative MPs are expecting;

Theresa May should give clear answers to whether she hopes Britain will remain in the customs union, and the single market, before negotiations begin;



Any deal should strive to avoid tariffs and other “regulatory and bureaucratic impediments” to free trade;

The government should seek to maintain “continuous, close cooperation” with the EU on security, foreign affairs and defence.

The MPs also say they will be calling for evidence on the issues raised in the resignation email sent by Sir Ivan Rogers, the UK’s most senior diplomat in Brussels, when he quit earlier this month citing “muddled thinking”.

Benn said: “We’re not asking the government to give away its red lines or negotiating fall-back positions, but we do want clarity on its broad aims given the significance and complexity of the negotiating task. This white paper must be published by mid-February to give parliament and the devolved governments time to scrutinise it.”

The committee, which took evidence in Sunderland and Aberdeen as well as Westminster, includes prominent figures from the leave campaign, including former ministers Michael Gove and Dominic Raab.

Gove, who was the co-chair of Vote Leave, asked at one of the committee’s early hearings about the possibility of a “quickie divorce” from the EU.

Some pro-Brexit MPs are sceptical about the need for a transitional deal, which they fear could unnecessarily prolong the process of leaving and make it harder for the UK to strike new trade deals with countries outside the EU.

But after hearing evidence from a series of business groups, senior Whitehall figures and policy experts, MPs from all sides of the debate signed up to the demand for a short-term arrangement to smooth Britain’s exit.

The report warns: “A ‘cliff edge’ change in circumstances could be extremely disruptive in some sectors to businesses both in the UK and in the EU 27.”

Benn said: “The government should seek appropriate transitional arrangements in the interests of business in the UK and the EU 27.”

The report stresses the complexity of the challenge the government faces, with two separate negotiations, potentially to be carried out in parallel – the divorce deal from the EU, including Britain’s share in financial commitments such as pensions, and the details of a new trading relationship.

It suggests the government should discuss carefully with the EU’s negotiating team how to phase the various aspects of the task.

Emma Reynolds, a Labour MP on the committee, said: “I think it is significant that we’ve reached agreement on this report.”