Trade unionists on both sides of the Irish border have said a “catastrophic” no-deal Brexit should be avoided at all costs.

Northern Ireland voted Remain in the Brexit referendum and the Irish Congress of Trade Unions (ICTU) gave a qualified response to Prime Minister Theresa May’s draft withdrawal deal.

It said if there had to be a divorce, it should be as soft as possible and added: “A UK-wide backstop with the entire UK in a customs union is preferable to a Northern Ireland-only backstop.

“We must insist that a no-deal scenario that sees the UK crash out of the EU at the end of March 2019 must be avoided at all costs and is unacceptable.

“The consequences of such a no-deal Brexit would be catastrophic.”

On Wednesday the leadership of the all-Ireland trade union movement at its executive meeting in Belfast considered its response to the draft agreement negotiated between the EU and UK.

It represents the interests of nearly 800,000 workers across the island of Ireland.

Owen Reidy, assistant general secretary at the Irish Congress of Trade Unions, was among those considering the draft withdrawal agreement (ICTU/PA).

The organisation said: “Given that unique cross-border perspective, we campaigned against Brexit. We remain firmly of the view that there is no such thing as a good Brexit for working people in Northern Ireland or in the Republic of Ireland.

“Any Brexit withdrawal agreement will still be less favourable than full UK membership of the EU for working people across these islands.

“The recent draft withdrawal agreement is essentially the end of the beginning of the UK isolating itself from the EU.

“It also remains to be seen if there is any real prospect of this proposed agreement commanding the support of the majority of MPs in the House of Commons.”

The trade union movement warned against a hardening of the border on the island of Ireland, creation of a border in the Irish Sea or an economic frontier between the islands.

“It is our view that the best way to achieve this is to negotiate as close as possible a relationship between the UK and the EU; preferably with the UK as a whole remaining in the Single Market and a Customs Union in the longer term.

“Only by achieving this can we arrive at a situation where the rights of citizens and workers, and where jobs and trade will not be impacted to a detrimental extent by this Brexit.”

Earlier this month, TUC general secretary Frances O’Grady accused the Conservatives of negotiating a “blindfold” Brexit deal which did not deliver for working people.