Boris Johnson has been blasted for “breaking” promises to Northern Ireland after his Brexit chief admitted he “underestimated” the chaos after leaving the EU.
Lord Frost confessed time is "starting to run out" to fix the problems with sending goods from Britain to Northern Ireland.
And he said the UK Government had "underestimated" the impact the Northern Ireland Protocol, which Mr Johnson negotiated as part of his original so-called ‘oven ready’ Brexit deal in 2019, would have on the country.
Another minister, Solicitor General Lucy Frazer, today admitted things were “more difficult than we anticipated”.
She told Sky News: “It is very difficult on the ground in terms of trade.
"It is really important that we sort it and Lord Frost is doing just that.
"As it has panned out, on the ground it is more difficult than we anticipated and we do need to sort out that trade arrangement."
There is growing tension between London, Belfast and Brussels to thrash out a solution after the Protocol led to turmoil in Northern Ireland - including the resignation of First Minister Arlene Foster.
The protocol has angered unionists by effectively creating a barrier between Great Britain and Northern Ireland.
That is because Northern Ireland continues to follow some EU customs and single market rules or checks to avoid needing a border with the Republic.
Talks are continuing between the EU and the UK Government to solve some of the issues - but many unionists have called for it to be scrapped.
Lord Frost claimed the government had "underestimated" the difficulty for businesses despite its own impact assessments making problems clear.
One assessment in October 2019 warned of “ongoing costs” of red tape and compliance for firms moving goods from Britain to Northern Ireland.
Shadow foreign secretary Lisa Nandy said the Government was "missing in action" on the issue of border controls in Northern Ireland.
"We've got to sort out the border in the Irish sea, not because Joe Biden has told us to but because it's causing absolute havoc in Northern Ireland and we've got a responsibility to get this right," she told Sky News.
"The Prime Minister made promises to the people of Northern Ireland that haven't been kept.
"I think the best way to resolve this is through decent relationships, investing in those relationships and through pragmatism.
"We need to make sure we minimise any kind of border checks or disruption, and we can do that with good will on both sides.
"But there's a feeling at the moment that the Government is missing in action on this, particularly the Prime Minister.
"Boris Johnson has created this problem and yet he's nowhere to be seen, I think there's a real feeling of dismay about that, but he could turn that around."
SNP President Michael Russell tweeted: "They didn’t 'underestimate'. They ignored all the warnings and despised those who gave them.
"I know because I heard and saw them - Frost & his deputy Appleby in particular - doing so at first hand."
US President Joe Biden is expected to tell Prime Minister Boris Johnson any trade deal with America would rely on the UK not reneging on the Northern Ireland Brexit deal.
The pair are due to hold talks before the G7 summit in Cornwall this week.
