UK prime minister Boris Johnson said he did not want to give a running commentary on Brexit talks when asked whether Northern Ireland would be leaving the EU customs union.

DUP opposition to a potential solution to the Brexit deadlock hardened last night as the EU and UK warned there was still a significant amount of work needed to reach a deal.

Hopes of a compromise being agreed in time for this week’s EU summit faded yesterday as sources in Brussels expressed deep scepticism that a compromise solution could be sufficiently developed in time to be put to EU leaders on Thursday or to MPs at a sitting of the House of Commons next Saturday.

Doubts about the complex proposal have put pressure on the timeline to secure a deal for the UK’s departure on October 31st and increase the possibility of a further Brexit delay to avoid a disorderly no-deal exit.

Continuing technical talks in Brussels on the proposal, already the subject of two days of intensive negotiations, could derail Mr Johnson’s plans to seal a deal with EU leaders at the summit on Thursday and Friday.

The delay increases the chances of another summit being held before the UK’s exit date.

The proposal emerged from a meeting last week between Taoiseach Leo Varadkar and UK prime minister Boris Johnson, leading the EU to intensify negotiations around the plan in a bid to break the Brexit impasse.

Mr Shannon said the proposed “double customs” solution would not work because it would treat Northern Ireland “differently” to Britain.

“It is simple. Are we being treated the same as England? No, we are not. Therefore, if we are not being treated the same as England, then we are not going to accept it,” he said.

Spotlight on DUP There has been considerable speculation since Mr Varadkar’s Brexit meeting with Mr Johnson on Wednesday about a compromise proposal where Northern Ireland would leave the EU customs unions but that the UK would operate EU customs and tariffs on goods moving between Britain and Northern Ireland.

This has turned the spotlight on whether the DUP could agree to arrangements that avoid customs controls on the island of Ireland.

DUP deputy leader Nigel Dodds told Italy’s La Repubblica newspaper that Northern Ireland “must stay in a full UK customs union, full stop”.

“It cannot work because Northern Ireland has to remain fully part of the UK customs union,” he said.

The European Commission said last night that “a lot of work remains to be done” following “constructive” technical talks with the UK over the weekend.

UK prime minister Boris Johnson told his cabinet that a last-minute deal was still possible but there was “still a significant amount of work to get through” and the UK must be prepared to leave without a deal.

The Government indicated that there were still significant obstacles yet to be overcome in the negotiations.

“Can we get this deal done [at EU level] by next Thursday or Friday? Will it require an extension of time even with goodwill on all sides?” Minister for Agriculture Michael Creed asked on RTÉ yesterday.

“And then can the UK government get it through when Theresa May previously failed to get [it] through? They are all significant questions with no clear answers at this stage.”