Downing Street still believes the Irish border problem can be resolved by December, despite Dublin’s threat to veto Brexit trade talks over the issue regardless of Theresa May’s £40bn divorce offer.

Ireland fired a warning shot on Tuesday by suggesting May’s enhanced financial offer to the EU was not enough on its own to secure the trade talks sought by the UK without guarantees that Brexit will not lead to a hard border.

But senior UK officials remain confident that Northern Ireland will not prove an insurmountable sticking point at the next EU council in December.

Whitehall sources said the UK would not countenance giving in to requests for Northern Ireland to stay in the customs union or single market – but that ministers believed some language could be agreed with the EU to guarantee no return to a hard border.

Simon Coveney, the Irish foreign minister, said an enhanced financial offer was not enough on its own to secure the UK the trade talks it is seeking.

He claimed there was “a lot of solidarity” among the EU27 for Ireland’s position that Northern Ireland must retain the regulatory framework of the single market and customs union in order to avoid creating a hard border.

He told the Evening Standard: “Anybody who thinks that just because the financial settlement issue gets resolved … that somehow Ireland will have a hand put on the shoulder and be told: ‘Look, it’s time to move on.’ Well, we’re not going to move on.

“This is a much bigger issue than trade. This is about division on the island of Ireland. I will not be an Irish foreign minister that presides over a negotiation which is not prioritising peace on the island of Ireland … We’re not willing to move on without more assurance on the border.”

Arlene Foster, the leader of Northern Ireland’s DUP, warned Ireland’s taoiseach, Leo Varadkar, to stop the “careless” threats over Brexit.

“I’m saying to him that he should know better than anybody that you don’t play around with Northern Ireland to effect change in other places, and actually what I would like to see the Irish government doing is working with Northern Ireland, working with the Westminster government, to bring about a Brexit that works for Northern Ireland but also for the Republic of Ireland,” she told the BBC.

Theresa May’s spokesman said the prime minister had been “engaged with the taoiseach throughout this process”. He said: “We are working hard to try and find that unique solution that we need to the situation on the border. We’re in a negotiation but, as I say, we think we’re making good progress, we think it’s in the interests of the UK and also of the EU27 to move these talks on, and that’s what we’re aiming to do as we get towards the December council.”

A mother reflects on Brexit’s consequences for Northern Ireland in Your Ma’s a Hard Brexit, a film made by the Guardian and Headlong

Earlier, Boris Johnson, the foreign secretary, said a return to a hard border was “unthinkable”. But MPs fighting against a hard Brexit warned that neither side had come up with a solution that could prevent a hard border if the UK insists on leaving the customs union and single market.

Pat McFadden, a Labour MP and leading supporter of Open Britain, said: “At the moment, ministers think they can leave the customs union and the single market and then blame the EU for the consequences of their decisions. But leaving the single market and customs union were decisions taken by Boris and his fellow Brexiteers for ideological reasons, and they were made without a second’s thought to the consequences for the Irish border.

“It is therefore in Boris’s hands, and those of his fellow ministers, to ensure there is no need for a hard border. The simplest way to do so would be to remain in the customs union, even if we are leaving the EU.”

The issue of the Irish border is one of three areas – along with the financial settlement and the rights of EU citizens – where the EU has demanded progress in Brexit talks in order to move to discussions on trade.

May has managed to get her cabinet to agree to increase the UK’s financial offer to around £40bn. However, it is still by no means certain that other EU states will agree enough progress has been made at the December council to allow the negotiators to start talking about trade.



Quick Guide What is the EU withdrawal bill? Show What is the EU withdrawal bill? The EU Withdrawal Bill – once known as the Great Repeal Bill – is going through the House of Commons to repeal the 1972 European Communities Act and transpose all existing EU legislation into domestic UK law, which will avoid a 'cliff-edge' change on the day after we leave the EU. Parts of the bill have been highly controversial, and MPs have tabled hundreds of amendments to try and change its wording, including a significant number of Conservative rebels. Some of the key controversies include its use of so-called Henry VIII powers, which will give government ministers the power to tweak the wording of laws to make sure they make sense in UK legislation - but those changes could take place without having to go through parliament. MPs have called this a "power grab" by the government. The government estimates around 800 to 1,000 measures called statutory instruments will be required to make sure the bill is applied correctly. Other concerns include the government's decision not to include the EU charter of fundamental rights in the law being transposed. Other amendments are attempts to affect the Brexit process, including legislating for a transitional period and giving MPs a binding meaningful vote on the deal secured by Theresa May, before the deal is finalised.

The EU is demanding more like £60bn from the UK but May’s proposal has caused a backlash among some of the hardest Brexit supporters in the Conservative party.

David Jones, a former Brexit minister, called for May to walk away from the talks if the EU refused to start discussing trade after the December council. He said: “The UK has shown outstanding patience and goodwill since serving the article 50 notice. It is high time the EU stopped its prevarication.

“If the prime minister does not receive confirmation that the EU will now start talking seriously about the future relationship, we should tell them we are suspending negotiations until they are ready to do so. There is nothing to be gained by continuing to flog a dead horse.

“We should also be making serious preparations for life outside the EU by investing in the personnel, infrastructure and IT needed to commence trading with the EU on World Trade Organization terms. Putting those arrangements in place will have the doubly beneficial effect of providing reassurance to business and signalling to the EU that we are not disposed to be strung along.”

