The European Union’s chief Brexit negotiator, Michel Barnier, has pledged support for the Irish border backstop regardless of what happens in the Brexit negotiations.

“The EU will stand fully behind Ireland,” Barnier said on Monday at a joint press conference with the taoiseach, Leo Varadkar, in Dublin.

Speaking in English to underline his point, Barnier said that if the UK were to leave without a deal the EU would still expect it to honour the backstop, an insurance policy to avert a hard border on the island of Ireland.

“You have our full support,” he said, looking at Varadkar. “The backstop is currently the only solution we have found to maintain the status quo on the island of Ireland ... Let me be very clear. We would not discuss anything with the UK until there is an agreement for Ireland and Northern Ireland as well as for citizens’ rights and financial settlement.”

It was a blunt warning to Westminster, which experienced another day of turmoil, that a no-deal exit would freeze trade talks until the Irish border issue was resolved. Some Brexiters have pinned hopes on the EU pressuring Ireland to drop the backstop.

The diplomat said the EU’s 27 member states remained fully united while the House of Commons debated the UK’s future relationship with the EU. “We want to respect the UK parliamentary debate ... we all hope that these talks will produce a positive outcome.”

The EU was willing to further clarify the political declaration that accompanies the withdrawal agreement should it help Westminster to reach agreement, he said. “Work can be done extremely quickly.”

Varadkar thanked Barnier for the expression of solidarity and said other EU members understood the need to protect the 1998 Good Friday agreement. “Should no deal arise, it will be a shared challenge.”

The taoiseach reiterated Ireland’s support for extending the Brexit deadline to help the UK make an orderly departure. He expressed confidence the EU would reach agreement at Wednesday’s European Council meeting of leaders.

Neither man took questions from the media.

It was Barnier’s fifth visit to Ireland as the EU’s chief negotiator. In addition to Varadkar he met Simon Coveney, the foreign minister, and Paschal Donohoe, the finance minister.

Earlier on Monday the Irish government published a no-deal notice spelling out the barriers facing farmers from Northern Ireland who export to food processing plants in the Republic.

Consignments of animals and animal products must be presented at the border inspection post at the point of first arrival in the EU to comply with EU rules, the notice said. This would present difficulties as the only border inspection posts in Ireland are in Dublin airport, Dublin port and Shannon airport.

Uncertainty over how to keep the border open while protecting the EU’s single market has not deterred across-the-board support in Ireland for the backstop.

Mark Durkan, a former leader of Northern Ireland’s SDLP who is now running as a Fine Gael candidate in Dublin for the European elections, launched a “back the backstop” campaign on Monday.