Mr Sunak’s government revealed new arrangements to remove routine checks on goods moving from Great Britain to Northern Ireland in a bid to restore power-sharing at Stormont.
Checks required under the previous so-called “green lane” will be further reduced – a tweak aimed at fixing some of the unresolved mess left by Mr Johnson’s Brexit deal.
Despite effectively being an extension of his own deal, Mr Johnson joined Tory rebels in claiming the new arrangements could thwart Britain’s post-Brexit “freedom” to diverge from EU rules.
The former PM – who has repeatedly criticised Mr Sunak since he was kicked out of No 10 – called on his successor to have the “courage” to ditch more Brussels regulations.
“We must retain the appetite and the courage to diverge from the low-growth high-regulation European model,” said Mr Johnson on X, formerly Twitter.
“We must at all costs avoid a return to anything remotely like the disastrous ‘Chequers’ formula, whereby artificial concerns about the border between Northern Ireland and Ireland are used to keep the whole of the UK in alignment with EU rules.”
Mr Johnson’s former Brexit negotiator Lord David Frost – believed to be part of a small cabal of right-wing MPs and ex-advisers plotting to bring down Mr Sunak – said he agreed with the former PM.
The trouble-making Tory peer warned that the new agreement with the DUP should not “slow” the push to diverge from the EU.
Under the new deal set out in Mr Sunak’s “Safeguarding the Union” paper, the “red lane” for transporting goods from GB to NI, and then on into the EU single market in the Republic of Ireland, will remain.
But routine checks will be removed from the “green lane” on goods from the GB destined to stay in NI, and replaced with only occasional checks when “smuggling and disease risks” are suspected.
The old “green lane” will be rebranded as the “UK internal market system”. And the government estimates that 80 per cent of goods will now move free of routine checks.
The government has pledged to amend domestic law – specifically a section of the European Union (Withdrawal) Act – to affirm the fact that new EU laws will not automatically apply in Northern Ireland, and must first be subject to oversight by Stormont.
In a bid to keep both the DUP and Brexiteers happy in allowing UK-wide divergence from EU standards, there is also a legal requirement that any new legislation is assessed as to whether it “impacts on trade between Northern Ireland and Great Britain”.
But some Brexiteer Tory MPs remain sceptical. Former home secretary Priti Patel and former business secretary Sir Jacob Rees-Mogg challenged Northern Ireland secretary Chris Heaton-Harris to explain how the UK would be able to diverge on EU rules without risking arrangements for Northern Ireland.
Answering their questions in the Commons, Mr Heaton-Harris insisted that the deal did not “change the freedoms and powers we have secured through Brexit”. The minister added: “It will not reduce our ability to diverge.”
But fellow right-winger Theresa Villiers – a former Northern Ireland secretary – said she was “troubled” by the deal and the prospect of it being rushed through parliament. “It is vital that there’s nothing in the deal which prevents Great Britain from diverging from EU rules,” she told The Telegraph.
However, DUP leader Jeffrey Donaldson has hailed the plan, claiming it would effectively scrap the contentious Irish Sea border for goods. “There should not be a border within the UK internal market,” he said. “These proposals remove that border.”
Sir Jeffrey praised Mr Sunak for going further than Mr Johnson. “Whilst Boris Johnson promised us a lot of things, he didn’t deliver them. Rishi Sunak has worked with us, [Mr Heaton-Harris] worked with us, to make these changes,” the DUP leader told the BBC.
The DUP has agreed to drop its two-year blockade of Stormont but there are those within the unionist party who remain deeply sceptical of the proposed agreement.
Sammy Wilson, the most outspoken, said the UK would still have to follow EU rules. “This is a result of this spineless, weak-kneed, Brexit-betraying government – refusing to take on the EU and its interference in Northern Ireland.”
Legislation promised in the deal is set to be fast-tracked through parliament on Thursday to enable the restoration of the institutions at Stormont – possibly as soon as Saturday.
No 10 has insisted that the DUP deal would not mean that the Windsor Framework agreement Mr Sunak struck with the EU Commission president Ursula von der Leyen would not have to be reopened.
Downing Street said on Wednesday that the deal contains “significant” changes to the Windsor deal’s “operation” but is not about altering the “fundamentals” of the framework.
The European Commission effectively endorsed the new arrangement by saying it had come “following in-depth technical discussions with the UK”. Vice-president Maros Sefcovic said on Wednesday that it “replies to the needs of Northern Ireland businesses while protecting our single market”.
And Micheal Martin, the Republic of Ireland’s deputy PM, does not expect the European Commission to object to the new Sunak plan, saying: “I do not anticipate any particular difficulties in respect of the EU side.”
It came as Tory minister Andrea Leadsom dismissed the concerns of business chiefs over the costly new checks imposed on EU imports – calling them the “price you pay” for Brexit.
The Brexiteer said on Times Radio that British firms must simply “adapt” to the new rules which began on Wednesday, and suggested they should even consider “changing their trading arrangements with the EU” if they were struggling.
Nigel Jenny from the Fresh Produce Consortium (FPC) warned that the checks for food and plant importers are essentially a £200m tax on the industry and would push up prices for consumers.
And Paolo Arrigo, managing director of London-based importer Seeds of Italy, told The Independent that the new checks were “anti-small business” and that it was now easier to import from China than France.