Lord William Hague, a former leader of the UK's ruling Conservative Party, has weighed into the Cabinet row over how Britain plans to split from the EU, it emerged on Tuesday 1 August.

Hague, who also served as Foreign Secretary under David Cameron, threw his support behind Chancellor Philip Hammond in an opinion piece for The Telegraph. The Tory grandee argued that Hammond, a Remain campaigner at the EU referendum, could "rescue" Brexit with a plan to keep the UK in the EU's customs union and single-market until 2022, three years after Britain officially splits from the bloc in 2019.

"What is quite obviously needed is an approach that cuts through all of these problems simultaneously; that reduces the need for rushed legislation, reassures the business world and commands wide support across Parliament. Is it possible to do that? Yes, and the Chancellor, Philip Hammond, deserves great credit for putting forward such an approach," Hague said.

"He has evidently been trying persuade his Cabinet colleagues that we should be seeking to stay in the EU single market and customs union during a transition and 'implementation' phased last to 2022, followed by a free trade deal with our former partners after that. This is seen by longstanding advocates of leaving as a 'soft' position or a climbdown. But in reality it is a plan to rescue Brexit from an approaching disaster."

He added: "This should, of course, be the plan of the whole government, agreed in advance and relayed unanimously. But even in the absence of that, it is the most sensible and workable approach."

Hammond is reportedly at odds with International Trade Secretary Liam Fox, who has denied that the Cabinet have agreed on a three-year-long transition phase. Such a move would prevent a crackdown on EU immigration and stop the UK brokering its own free trade agreements with non-EU nations.

Number 10 said on 31 July that it would be "wrong" to suggest that EU free movement to the UK would "continue as it is now" after 2019. But Home Secretary Amber Rudd has said that EU nationals will be able to continue to come to the UK during a post-March 2019 transition period so long as they go through a "registration and documentation" process.

The senior Conservative has also commissioned a group of top economists, the Migration Advisory Committee (MAC), to investigate how the UK's future immigration system "should be aligned with a modern industrial strategy".

The MAC, which is chaired by Professor Alan Manning, has been given a deadline of September 2018 to report back to Rudd.

"This is an important and extensive commission and the MAC welcome the opportunity to contribute to the UK's knowledge base in this area at this critical time," Manning said. "The MAC will research and analyse the areas covered by the questions using all available data sources, using both internal and external analysts and expertise."