Tánaiste and Minister for Foreign Affairs Simon Coveney has discussed the lack of progress in the Brexit negotiations with British Chancellor Philip Hammond and Northern Ireland Secretary of State Karen Bradley in London.
Mr Coveney met British Environment Secretary Michael Gove and Labour Party spokesperson on Brexit Keir Starmer.
The Tánaiste reaffirmed the position of the Government and the European Union on the need for progress on the border, and for the UK to deliver legally on the commitments it made last December.
His trip came ahead of a crunch meeting of the British cabinet on Friday, at which new proposals for custom arrangements post-Brexit will be discussed.
Meanwhile, Sinn Féin's leader in Northern Ireland has said the British government is more focused on its "internal negotiation" than talks on addressing the border issue.
Michelle O'Neill said any return of physical infrastructure at the border between Northern Ireland and the Republic of Ireland after Brexit would be a security threat and have "serious implications" for business.
She hit out at the lack of progress on addressing the issue ahead of the prime minister's crunch meeting with her Cabinet.
Speaking on BBC Radio 4's Today programme, she said: "I welcome the commitment to no hard border on the island of Ireland; however, I am yet to see a plan to prevent that happening.
"I think that's been the most disappointing thing throughout the whole of the Brexit negotiations to date."
Ms O'Neill said that the British government is "dealing with its own internal negotiation as opposed to the negotiation about actually what the future looks like.
"Brexit is catastrophic for the island of Ireland, there is no doubt," she said. She also called for a special status for Northern Ireland which would see it remain in the single market and customs union.
Claims pro-Brexit campaign group may have broken spending rules
Britain's Electoral Commission is preparing to find the official campaign to leave the European Union guilty of breaking election law during the 2016 referendum, according to the former chief executive of the group.
Matthew Elliott, former chief executive of Vote Leave, said the Electoral Commission had concluded in a draft investigation that Vote Leave exceeded spending limits.
But Mr Elliott told Sky News the Electoral Commission had committed a "huge breach of natural justice" by only listening to "the fantasists", alleging that the watchdog had not listened to Vote Leave's version of events.
This follows allegations by a former employee of Vote Leave that the group made a donation of £625,000 to another Brexit campaign group, Be Leave, meant it violated spending rules because the groups worked together.
"Their initial conclusion is that we have overspent, that a donation we made to another group during the course of the campaign was incorrect, we shouldn't have made that donation," Mr Elliott told Sky News.
The Electoral Commission said in a statement that Vote Leave had taken the "unusual step" of going public with the findings of its draft report.
"The Commission will give due consideration to the representations made," the commission said.
"We will then, at the earliest opportunity, publish a thorough and detailed closing report in order to provide a full and balanced account to the public and to parliament."
In the 2016 referendum, 17.4 million voters, or 51.9%, backed leaving the EU while 16.1 million voters, or 48.1%, backed staying.