The prime minister, who faces an uphill battle to get the controversial deal through Parliament, has been accused by the Orange Institution of “betraying the unionist community” in Northern Ireland.

Despite many of the Province’s business, farming and fisheries industry leaders backing the Brexit deal, unionist politicians have said they cannot support it as it could threaten the very future of the Union.

Now the Grand Orange Lodge of Ireland (GOLI), which remained neutral regarding the EU referendum in 2016, has spoken out against what it describes as “a poor deal which goes back on the assurances offered by the prime minister throughout this process”.

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Prime Minister Theresa May making a statement in the House of Commons on Brexit yesterday

“On consideration of the current proposed withdrawal agreement, it is evident that it does not rule out a future regulatory border in the Irish Sea, thereby making Northern Ireland a place apart. Such a development would have the inevitable impact of diminishing the constitutional integrity of the United Kingdom,” a GOLI statement said.

“Whilst uncertainty abounds regarding a no-deal scenario, the people of Northern Ireland should not be expected to accept a poor deal which goes back on the assurances offered by the prime minister throughout this process.

“We recognise that many in the business sector have given the withdrawal proposals their support. We also recognise that within our own organisation there are business owners, farmers and fishermen – none of whom want to see their own financial interests injured as a result of a failure to formulate an agreed way forward.

“As a stakeholder in local society, we too wish to see a settled, prosperous and confident Northern Ireland. It appears, however, that in ensuring a frictionless north-south border (which accounts for around £2bn per year of inward trade to NI) the current proposals lose sight of the financial risk of creating new checks and controls on inward goods from the rest of the United Kingdom – recently valued at £11.6bn per year.”

The Grand Orange Lodge of Irelands headquarters at Schomberg House, Cregagh Road, Belfast

The statement continued: “Despite a recent meeting with Northern Ireland Office officials, and examination of the aspirational and non-binding ‘Political Declaration’, we remain unconvinced that the current proposed agreement is a good deal for Northern Ireland – economically or constitutionally.

“The backstop may only be deployed as a worst-case scenario – but whilst it continues to be an option, it continues to place the future legal and constitutional position of Northern Ireland in question. As such, we believe it threatens the Union.

“It should come as no surprise that this institution will never be neutral on the Union.”