There is near-unanimous political outrage in Ireland over a leaked British government plan to throw up a “buffer zone” with customs posts on the Irish border. Parties across the political spectrum branded it “out of the question”.

Secret proposals presented to Brussels suggested building vast “customs processing centres” along the frontier as a replacement for the Brexit backstop. Irish public broadcaster RTE reports that the plan was included in “non-papers” presented to Commission negotiators.

The ideas represent a significant reversal by the UK government on commitments made under Theresa May to avoid “checks and controls” between the two territories to preserve the Northern Ireland peace process.

Ireland’s foreign minister Simon Coveney said that the proposals were a “non-starter”.

“Time the EU had a serious proposal from the UK government if a Brexit deal is to be achievable in October. Northern Ireland and Ireland deserves better!” he tweeted.

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Irelands main opposition party Fianna Fail also immediately rejected the idea.

“This is effectively a border with a buffer zone and is clearly not a satisfactory alternative to the backstop,” said Lisa Chambers, the group’s Brexit spokesperson.

“With 30 days now to go until Brexit we need to see sensible workable solutions that ensure no hard border on the island of Ireland. What about regulations on goods?”

Uniting Ireland’s political parties in condemnation, Sinn Fein leader Mary Lou McDonald said: “The British proposal to reimpose a hard border on our island, as reported by RTE, is out of the question. It is further evidence of Tory recklessness and belligerence towards Ireland.”

Downing Street appeared to beat a hasty retreat from the plans, with Boris Johnson going on television to say they would not be in the final proposals unveiled later this month.

Speaking in the Irish parliament, Taoiseach Leo Varadkar said he "welcomed" the fact the prime minister had disowned the plans.

"Had he not, in my view, it would be hard evidence of bad faith by the UK government," he added.

UK sources have said the government will unveil concrete proposals to replace the backstop after the Conservative party conference this week is over – apparently to minimise the political impact on the government.

Technical talks continue in Brussels between the two teams on how to replace the backstop, which Boris Johnson has said he cannot accept – but the UK has insisted on keeping its initial proposals secret for the duration of discussions.

Ireland’s deputy prime minister and foreign minister Simon Coveney (PA)

Earlier this week EU diplomats warned that Mr Johnson’s approach appeared to be “kamikaze” and that there was a still a huge gulf between the two parties.

An Irish government spokesperson said: “The EU task force has indicated that any non-papers it has received from the UK to date fall well short of the agreed aims and objectives of the backstop. The UK’s non-papers were given to the task force on the strict understanding they would not be shared with anyone. The taskforce has said it has received no credible proposals from the British.