Boris Johnson has accused the European Union and Remainers of using the Irish border issue to try to frustrate Brexit.
The Foreign Secretary said Brussels and anti-Brexit politicians were attempting to keep Britain in the customs union, "effectively the single market", by saying it is the only way to avoid a hard Irish border.
It comes after a letter sent by Mr Johnson to Theresa May emerged, saying the Government should focus on preventing the frontier becoming "significantly" harder, reigniting a row over the issue.
With the EU preparing to set out on Wednesday draft legal plans to ensure Northern Ireland is aligned with Brussels rules if no other solution can be found to avoid a hard border with the Republic, Mr Johnson hit out at the "inverted pyramid of objections" over the issue.
Speaking to reporters after returning from a jog in the snow, he said: "What is going on at the moment is that the issue of the Northern Irish border is being used quite a lot politically to try and keep the UK in the customs union - effectively the single market - so we cannot really leave the EU. That is what is going on."
Mr Johnson said his letter showed "there are very good solutions" that would prevent a hard border for goods crossing the Irish border, while "allowing the UK to come out of the customs union, take back control of our tariffs schedules, take back control of our commercial policy, take back control of our regulation".
"It is a very positive letter," he added.
The former London mayor also repeated widely criticised comments likening the Irish border to congestion charge zones in the capital, asking a reporter: "I don't know whether you have ever driven into the congestion charge zone from outside the congestion charge zone - have you?
"Do you slow down? Do you feel any let or hindrance? Do you check your progress? Do you brake? Do you?"
Brussels' chief negotiator, Michel Barnier, said there would be "no surprises" in the 120-page draft document, which will cover the political agreements reached between Mrs May and Commission president Jean-Claude Juncker in December.
Taoiseach Leo Varadkar said he is satisfied the legal text will ensure there will be no hard border on the island of Ireland after Brexit.
But in a suggestion that the phrasing of the document may cause problems in Westminster - where the Democratic Unionist Party props up the Prime Minister's minority Government - he said: "We cannot automatically assume it will be acceptable to the United Kingdom or acceptable to all the parties in Northern Ireland so we could have an interesting few weeks ahead of us."
The UK Government has set out three ways to avoid a hard border - resolving the issue as part of a new trade relationship with the EU, specific technological solutions to the issue or - as a fallback option - regulatory alignment with EU rules to protect economic co-operation and the Good Friday Agreement.
But a memo sent by Mr Johnson to the Prime Minister and other members of the Brexit war cabinet appeared to suggest a hard border remained a possibility, and would not be as damaging as feared.
The document, obtained by Sky News, said "it is wrong to see the task as maintaining 'no border'" on the island of Ireland and the Government's aim will be to "stop this border becoming significantly harder".
Downing Street was swift to play down Mr Johnson's comments.
A source said: "We agree the task isn't about no border, it's about no hard border."
The 18-page document was circulated to members of the Brexit Cabinet sub-committee before the Chequers meeting where senior ministers agreed on the approach to the next phase of talks, which Mrs May will set out on Friday.
Former Brexit minister David Jones said the EU's proposal was "completely unacceptable" and amounted to an attempt to annex Northern Ireland.
The Leave-backing Tory MP told BBC Radio 4's Today programme: "What is proposed is that Northern Ireland should remain part of the customs union, it should effectively be part of the single market, and should, I understand, remain subject to the European Court of Justice. That effectively amounts to an annexure of Northern Ireland by the European Union."
He said the EU's plan would risk peace in Northern Ireland: "I think that it would be pretty catastrophic and I think that the European Union in actually proposing this is behaving wholly irresponsibly."