Downing Street has been forced to stress that Rishi Sunak’s hailing of Northern Ireland’s access to both EU and British markets should not be seen as an endorsement of single market benefits for the whole of the UK.

During a visit to a Coca-Cola factory in County Antrim to promote his Windsor Framework, the Prime Minister said the deal would create “the world’s most exciting economic zone”.

“If we get this right, if we get this framework implemented, if we get the Executive back up and running here, Northern Ireland is in the unbelievably special position – unique position in the entire world, European continent – in having privileged access, not just to the UK home market, which is enormous, but also the European Union single market.

“Nobody else has that. No-one. Only you guys: only here, and that is the prize.”

Critics online were swift to point out that the entire UK had full access to the EU’s single market before Brexit.

The anti-Brexit campaign Best for Britain tweeted: “Sunak in Belfast (sic) emphasises what ‘a hugely privileged position’ it is to have access to both EU and UK markets, and how it is definitely worth the relatively small trade-off of following some Brussels regulation.

“Why not extend this ‘fantastic deal’ to the whole country? Oh.”

Stella Creasy, chairwoman of the Labour Movement for Europe, said: “The Prime Minister is boasting about the benefits of the single market and customs union for businesses in Northern Ireland, whilst denying those same benefits to businesses struggling in the rest of the UK with our current economic crisis.”

The Walthamstow MP said “we do need to remind those who brag about Brexit” of the “real cost to our economy and our country it has created”.

Mr Sunak’s remarks could also anger hardline Eurosceptics in his own party, who may interpret them as a secret wish by the Prime Minister to move towards closer trading ties with the bloc.

Pressed on the issue later, the Prime Minister’s official spokesman told reporters: “The British people made a decision in 2016 and we are seeing the benefits of that decision, whether that’s in the ability to change our environment laws, some of the tax elements the Prime Minister talked about just today, in fact.

“With regards to Northern Ireland, it is simply a fact that because of our respect for the Good Friday Agreement and the central importance: Northern Ireland’s unique position means it needs to have access to both markets, not least to avoid a border on the island of Ireland, which nobody wants to see.

“That puts it in a unique position and what the framework does is finally cement those capabilities.”