The Government and the European Union on Monday night rubbished leaked British proposals to establish customs posts on both sides of the Border after Brexit.

Senior sources in Dublin and Brussels dismissed completely the British ideas, contained in papers tabled in talks with EU negotiators and reported by RTÉ on Monday night, and said they showed there was little if any chance of a breakthrough in the talks.

The European Commission declined to comment on the reports, while the Irish Government said it has “yet to see any credible alternatives to the backstop”.

RTÉ reported that the British ideas were contained in “non-papers” – documents tabled for discussion purposes – submitted to the EU in recent weeks. They would mean a string of “customs clearance sites” established on both sides of the Border to manage the flow of goods between North and South.

Some Government sources in Dublin were incredulous at news of the British proposals. But others said they demonstrate that the chances of any new agreement with the UK before an EU summit later this month is negligible.

Opposition politicians in Dublin rejected flatly the proposals while US congressman Brendan Boyle – who has with other members of the Irish-American lobby in Washington threatened to veto any US-UK trade deal if Brexit leads to the return of a hard border – criticised the plan as “reckless”.

Labour Party MP Keir Stamer, commenting on social media, said if British prime minister Boris Johnson had spent any time listening to businesses and communities in Northern Ireland “he would know that these proposals are utterly unworkable”.

Democratic Unionist Party leader Arlene Foster: Moved to quash speculation that the DUP would support a time-limited backstop. Photograph: Ben Stansall/AFP

What chance a Brexit impasse?

Prospects for any new Brexit agreement also seemed remote at the Conservative Party conference in Manchester.

Democratic Unionist Party leader Arlene Foster moved to quash speculation that the DUP would support a time-limited backstop, while the Government here rejected it as a way out of the Brexit impasse.

Ms Foster clarified remarks she had made when she said the DUP was willing to look at any proposal for a time-limited backstop.

“When asked a direct question I said I would look at a time limit. That’s a world away from saying that we were now advocating that,” she said.

Several senior Irish sources dismissed the idea that a time limit on the backstop could bridge the gulf between the British and EU positions. They said the idea was rejected earlier this year when pushed by Theresa May’s government.