DUP leader Arlene Foster accused Boris Johnson today of breaking his word over Irish Sea customs checks after Brexit and said that she cannot trust him again.

Ms Foster said customs officials told her there would have to be checks at the Irish Sea, contrary to the Prime Minister’s promises that there would be no hard border after Britain leaves the European Union.

On Friday Labour leader Jeremy Corbyn revealed leaked Treasury documents that showed that “at minimum” there would be extra paperwork for trade between the north of Ireland and Britain.

The Tories’ own Brexit Secretary Stephen Barclay has also indicated there will be checks.

Fears of a border in the Irish Sea were among the reasons that led 10 DUP MPs — who have propped up the Conservative government since Theresa May was PM — to vote against Mr Johnson’s withdrawal agreement.

Asked if Mr Johnson’s Brexit deal represented a “betrayal,” Ms Foster told the BBC’s Today programme: “I think it says more about the person who broke their word than me and the leadership of the … Democratic Unionist Party.”

When asked if she would be prepared to take Mr Johnson at his word in future, she said: “Well, once bitten, twice shy. We will certainly be looking for the detail of what this is going to look like.”

On Sunday, Mr Johnson admitted that there would have to be some checks on goods travelling from Britain to north of Ireland if they were then moving on to the Republic. But he continued to insist that his Brexit deal will not create friction in trading across the Irish Sea.