Sir Keir Starmer will on Monday signal that Labour is willing to fight Boris Johnson over his Brexit legacy at the next election, setting out a five-point plan to tackle the economic pain caused by Britain’s EU exit.

In a big tactical shift, Starmer will use a speech to denounce the “mess” created by the UK prime minister’s 2020 Brexit deal and the breakdown of trust with the EU caused by the row over the trading arrangements for Northern Ireland.

The Labour leader has until now shied away from talking about Brexit, fearing it would alienate Leave voters, but he has been emboldened by emerging evidence of the hit the departure has inflicted on the economy.

He will claim that Labour can “make Brexit work”, arguing that Johnson’s Brexit deal had contributed to a sense of a country that was “stuck”, with wages and growth stagnating and broken public services.

“They have created a hulking ‘fatberg’ of red tape,” he will say in a speech, comparing Brexit to the “wet wipe island” found in the river Thames. “It is hampering the flow of British business — we will break that barrier down.”

Brexit had become something of a taboo subject for Labour’s leadership: one-third of Labour supporters voted Leave in 2016 and Starmer was associated with the ill-fated campaign to overturn that result.

But new data has started to separate the economic effects of Brexit from the Covid pandemic, showing a dismal UK performance for trade and investment compared with other G7 countries.

An Ipsos UK study found last week the proportion of Britons who think Brexit has made their daily life worse has risen from 30 per cent in June 2021 to 45 per cent; only 17 per cent said their lives had been made better.

Starmer will insist that a Labour government would not seek to rejoin the EU’s single market or customs union or reintroduce freedom of movement — let alone seek to reverse the 2016 Leave vote.

“Nothing about revisiting those rows will help stimulate growth or bring down food prices or help British business thrive in the modern world — it would simply be a recipe for more division,” he will say.

Labour would seek a veterinary agreement with the EU to cut onerous agrifood checks, mutual recognition of product standards and a deal on mobility to facilitate short business trips and help artists tour in Europe.

Starmer would use the agrifood deal to remove most checks on trade between Great Britain and Northern Ireland and negotiate a trusted trader scheme to end the stand-off with Brussels over the rules, contained in the part of the Brexit deal called the Northern Ireland Protocol.

The Labour leader said business leaders wanted to safeguard the protocol, which leaves Northern Ireland in the single market for goods. “The solutions are there, the desire is there — what is lacking is trust,” he will say.

The German and Irish foreign ministers on Sunday wrote an opinion article in The Observer accusing Johnson of not engaging with Brussels on the protocol in “good faith”. They wrote there was no “legal or political justification” for his decision to introduce legislation to rip up parts of the agreement.

Starmer will say Labour would negotiate mutual recognition of professional qualifications and keep Britain in EU science programmes, including the €95bn Horizon scheme, which is cherished by UK researchers.

Data adequacy rules would be aligned but Starmer would follow Johnson in pursuing a different course on City regulation, he will say in an address to the Centre for European Reform.

The plan would also include more co-operation with the EU on justice and police matters including a new “security pact”.

Johnson is likely to portray Starmer’s speech as evidence of Labour wanting to unpick Brexit, a policy that was embraced by many working class voters in the former “red wall” in northern England.

Some senior Labour figures, including London mayor Sadiq Khan, want Starmer to go further and to commit to rejoining the EU single market, but that has been ruled out by party strategists.

Even the Liberal Democrats, who favour a return to the single market, have not set any timetable for the move, reluctant to re-engage the British public in a debate whose scars remain unhealed.