Hammond said that under World Trade Organization rules, London would have no choice but to reinstate checks | Christopher Furlong/Getty Images Philip Hammond: UK will enforce hard border in Ireland if there is no Brexit deal The chancellor’s words appear to undermine the official government position.

BIRMINGHAM, England — Britain would have to enforce controls on the Irish border if the U.K. leaves the European Union without a deal, Chancellor Philip Hammond said Monday.

In remarks that appear to undermine the official government position that the U.K. will do all it can to avoid border checks after Brexit, Hammond said that under World Trade Organization rules, London would have no choice but to reinstate checks.

Speaking at a fringe event at the Conservative Party conference in Birmingham, Hammond said: “The challenges around the Irish border are around the legal requirements we will have if we are not in a trade bloc within the European Union to operate the WTO-compliant border, which does require checks at the border. That’s what the WTO rules require."

"We are depending on the WTO to regulate our relations with the rest of the world, we will have to comply with the rest of WTO regulations or we will find we can’t enforce our WTO rights against others," he said.

Hammond's remarks are in stark contrast to Prime Minister Theresa May's refusal to answer the question in her interview with the BBC's Andrew Marr Show on Sunday.

Asked if she could guarantee there will not be a hard border in Ireland in the event of a no-deal Brexit, May said: "We are working to make sure that we leave with a good deal. That’s what my focus is on."

Pressed again, she replied: "If we leave — if we get to the point of no deal, we’re making the preparations because we don’t know what’s going to come out of the negotiations. If we leave with no deal, we as the United Kingdom government are still committed to doing everything we can to ensure there is no hard border between Northern Ireland and Ireland."

The confirmation from Hammond that the U.K. would be forced to reinstall border controls on the island of Ireland will be met with dismay by Brexiteers who insist Britain could simply refuse to enforce border controls, leaving Dublin with the choice of whether or not to put up barriers.

It also raises the stakes in the Brexit negotiations because any hard border between Northern Ireland and the Republic is a significant threat to the peace process, undermining the Good Friday Agreement.