Boris Johnson’s secret plans to solve the Irish border Brexit challenge involve customs sites on both sides of the border and real-time tracking devices on lorries, it has been reported.

The ideas, which mark a departure from his promise not to put infrastructure on the border, are part of four unofficial papers submitted by the UK to Brussels by Johnson’s team.

The broadcaster RTÉ, which has had sight of the the tightly guarded proposals, is reporting that customs clearance sites would be sited five to 10 miles from the border to the north and the south to deal with imports and exports.

Traders would have the choice of lodging their papers at these sites, similar to the ones that existed before the single market came into existence, or electing to be tracked electronically in an online “transit” arrangement.

The idea of permanent clearance sites on both sides of the border, even five to 10 miles away, and real-time tracking of the movements of goods are unlikely to be supported by the Irish government.

A spokesman for Downing Street said: “Nothing we are proposing involves checks or controls at the border. That is an absolute commitment.”

A government source said the report was a misrepresentation of the “non-paper”, which discussed customs checks at place of origin or destination of goods.

Quick Guide Why is the Irish border a stumbling block for Brexit? Show Counties and customs Inside the EU, both Ireland and Northern Ireland are part of the single market and customs union so share the same regulations and standards, allowing a soft or invisible border between the two.

Britain’s exit from the EU – taking Northern Ireland with it – risks a return to a hard or policed border. The only way to avoid this post-Brexit is for regulations on both sides to remain more or less the same in key areas including food, animal welfare, medicines and product safety. The 'backstop' in Theresa May's Withdrawal Agreement was intended to address this - stating that if no future trade agreement could be reached between the EU and the UK, then rules and regulations would stay as they are. This has been rejected by Brexit supporters as a 'trap' to keep the UK in the EU's customs union, which would prevent the UK striking its own independent trade deals. There are an estimated 72m road vehicle crossings a year between Northern Ireland and the Republic of Ireland, and about 14% of those crossings are consignments of goods, some of which may cross the border several times before they reach a consumer. Brexit supporters say this can be managed by doing checks on goods away from the border, but critics say it will be difficult to police this without any physical infrastructure like border posts or cameras, which could raise tensions in the divided communities of Ireland.

Interactive: A typical hour in the life of the Irish border Photograph: Design Pics Inc/Design Pics RF

In the limited cases that inspections were needed, physical checks could be at dedicated premises, factories or production sites, the source suggested.

But Simon Coveney, Ireland’s deputy prime minister, dismissed the proposals as a “non-starter”, and called for a “serious proposal” from the UK.

Non-Paper = Non-Starter. Time the EU had a serious proposal from the UK Govt if a #Brexit deal is to be achievable in October. NI and IRE deserves better! — Simon Coveney (@simoncoveney) September 30, 2019

Sinn Féin in Ireland and the Social Democratic and Labour party in Northern Ireland also dismissed the plans on Monday night. Sinn Féin president Mary Lou McDonald said they were “absolutely out of the question”, while SDLP leader Colum Eastwood said: “It doesn’t matter if it’s a mile, five miles or 10 miles away, the presence of physical checks will create economic and security challenges that are unacceptable.”

Labour said the proposals were “utterly unworkable”. Sir Keir Starmer, the shadow Brexit secretary, said: “They would place an enormous administrative burden on businesses and rely on technology that does not yet exist.

“Crucially, if true, they represent a rowing back on the commitments made to the people of Northern Ireland two years ago that there would be no return to a hard border or related checks or controls.”

The leak comes as Johnson puts his finishing touches on formal written proposals expected to go to Brussels in the next week for a revised Brexit deal.

Although all the indications are that a large gap remains in thinking, signs have emerged that the hardline position of the Conservative party’s most Eurosceptic backbenchers has softened just days before Boris Johnson’s team are due to enter a “tunnel” of secret negotiations with Brussels.

Mark Francois, the deputy chair of the European Research Group, has opened the door to a potential Brexit deal, indicating he would look at one even if it included a version of the controversial Irish border backstop to which the Eurosceptic ERG was once implacably opposed.

During a heated and sometimes bad-tempered event on the party conference fringe, he indicated that the “Spartan” wing of the party was in the mood for a deal.

“It has been sometimes been said that we will vote against anything regardless. That’s not true,” he said referring to the bloc of 28 backbenchers who voted against Theresa May’s Brexit deal three times.

“If there is some form of deal, be it over the backstop or anything else, then I and my colleagues will look at it and read it very carefully, because at the end of the day you are talking about international treaty law. So I’ll look at a deal if there is one,” he said.

Francois’ comments were seen as a subtle shift in approach for the ERG, whose support could unlock a deal for Johnson.

Q&A What is a Northern Ireland-only backstop? Show The British government’s version of Brexit involves the UK ultimately leaving the single market and customs union, requiring the return of a range of checks on goods crossing the border between Northern Ireland and the Republic of Ireland. The “backstop” is intended as a standstill placeholder to ensure such checks do not have to be imposed between Brexit happening with a deal, and the start of a new free trade agreement yet to be negotiated between the UK and the EU. Theresa May's withdrawal agreement proposed keeping the whole of the UK in a shared customs territory with the EU during this period. An alternative idea involves only Northern Ireland staying in the EU’s customs territory. That would place a customs border in the Irish Sea. May described it as a threat to the constitutional integrity of the UK, but the new prime minister, Boris Johnson, has opened the current talks by proposing an all-Ireland agri-food zone. The suggestion is that he will seek to quietly build on that with further NI-only arrangements. Given an NI-only backstop was an EU proposal in the first place, the U-turn would be warmly welcomed in Brussels, although attempts to give the Northern Ireland assembly a veto on its continuation would not be acceptable, and the DUP would be unlikely to support the prime minister in such a move in parliament. If there is a no-deal Brexit, then there is no backstop. Daniel Boffey

As recently as August, the de facto whip of the ERG warned that Johnson must honour his promise to kill off Theresa May’s deal completely.

Johnson has publicly said May’s withdrawal agreement is dead but the formal proposals, due to go to the EU next week, are expected to revolve around a revised backstop for Northern Ireland involving an agreement for agri-food on the island of Ireland and a possible time limit on the other elements of the backstop.

“My acid test will be: does it mean we genuinely leave the EU?” Francois told a meeting organised by the Eurosceptic thinktank Bruges Group.

He said his support for a deal “rather depends what’s in it … As a so-called Spartan, if it means we genuinely leave the EU, if it means we genuinely leave on Halloween, I will be the first in the aye lobby. If it really means we don’t, then I will vote against it and if we don’t no amount of browbeating will make me change my mind.”

His remarks follow weeks of shifting mood over the Irish backstop. The Democratic Unionist party, which was implacably opposed to the backstop, has also indicated it was in the mood for a deal. It is understood that the DUP has been consulted on the plans that Johnson is to take to Brussels next week.

Ireland’s prime minister, Leo Varadkar, also hinted last week that there could be amendments to the withdrawal agreement but warned there was still a huge gap between the UK and Irish positions.

The DUP leader, Arlene Foster, said she would look at the possibility of a backstop with a time limit but warned that agreeing to consider one was not the same as “advocating” one.

She told the Bruges Group: “It would be good to get rid of the iniquitous backstop” but added that it would be “good to get a deal”.

She called for space to be given to negotiators, who now have fewer than 17 days to come up with a deal before the next EU summit.