The UK has given written commitments last December and March that the withdrawal agreement will give a legal guarantee of no return to a hard border in Ireland in any circumstance, the Department of Foreign Affairs has said.
A spokesperson said this is the backstop, following reports in The Sunday Times that an all-UK customs deal will be written into the legally binding agreement governing Britain's withdrawal from the EU to avoid the need for an Irish backstop.
The Sunday Times report has been described as "speculation" by Downing Street.
The report says the plan would avoid the need to treat Northern Ireland differently, which has been the main stumbling block to securing an agreement on Britain's exit from the bloc, due to happen in March 2019.
The EU has reportedly suggested that a backstop post-Brexit customs arrangement covering all of the UK could give Britain some scope to set trade rules, while keeping Northern Ireland aligned with the EU.
British Prime Minister Theresa May's cabinet is to meet on Tuesday to discuss her plan, and she hopes there would be enough progress by Friday for the EU to announce a special summit, The Sunday Times said.
Preparations for a final deal are "far more advanced than previously disclosed", the report said, and will lead to a document of 50 pages or more being published.
The spokesperson said the article is obviously aimed at a UK audience, claiming that EU support to Ireland has been and remains unwavering.
They added that "Donald Tusk, Michel Barnier, Jean-Claude Juncker and indeed Theresa May herself have all said there will not be a deal without a legal guarantee of no hard border in Ireland."
Asked about the report, a spokesman at British Prime Minister Theresa May's office said:
"This is all speculation. The Prime Minister has been clear that we are making good progress on the future relationship and 95% of the withdrawal agreement is now settled and negotiations are ongoing."
Meanwhile more than 70 business figures are calling for a public vote on the final terms of Britain's exit from the European Union, warning that the country faces "either a blindfold or a destructive hard Brexit".
The letter argues that both the British government's current plans for Brexit, and a no-deal Brexit, would leave the country worse off than they were being in the EU if the country left in March.