The prime minister’s proposed EU withdrawal deal is “not Brexit for Northern Ireland”, says Nigel Dodds.
Speaking as the Commons prepared for a rare Saturday sitting, the DUP deputy leader said of his party: “We’ll be voting against the plan.”
Boris Johnson will now try to get his deal across the line without the support of the DUP’s 10 MPs.
Mr Dodds said he wanted to get a Brexit done that “works for the whole United Kingdom”.
“Our clear position is that we could not support a deal which puts a customs border down the Irish Sea – that’s always been clear from day one,” he added.
Sammy Wilson, the DUP’s Brexit spokesman, said on Friday that his party was talking to Conservative MPs in a bid to vote down Mr Johnson’s plan.
On Saturday morning, he met with members of the Eurosceptic European Research Group (ERG), who have encouraged their members to support the deal.
Mr Wilson has said the DUP was urging Tory MPs to “take a stand” with them.
Independent unionist MP for North Down, Lady Hermon, has not indicated whether she will support the government’s plan.
A number of Conservative MPs in the ERG have supported the DUP’s stance on Brexit in the past – but it is not clear if any of them will vote against the government this time.
Before the vote on the deal can go ahead, MPs will vote on an amendment – tabled by Oliver Letwin – that would withhold approval of the deal until the legislation to enact it was safely passed – a move that would automatically trigger the “Benn Act” and force the prime minister to request a further postponement of Brexit until 31 January.
Speaking on BBC Radio 4’s Today programme, Nigel Dodds described the Letwin amendment as “very interesting” and said the party would “look at that very closely and examine it”.
“What it may do is ensure that there is proper examination of all the details and allow a proper exploration of some of the statements that are being made about this withdrawal Brexit deal,” said Mr Dodds.
The BBC understands if the Letwin amendment is passed, the government plans to hold a vote on the entire Withdrawal Agreement Bill on Tuesday.
What does the deal involve for NI?
The new Brexit deal would involve Stormont giving ongoing consent to any special arrangements for Northern Ireland via a straight majority.
Pro-EU parties have a narrow majority at Stormont and there would be no unionist veto, as demanded by the DUP.
Northern Ireland would continue to follow EU rules on food safety and product standards and would also leave the EU customs union.
But EU customs procedures would still apply on goods coming into Northern Ireland from Great Britain in order to avoid checks at the border.
Stormont would have to approve those arrangements on an ongoing basis.
Approval would involve a straight-forward majority, which would keep the special arrangements in place for four years.
Alternatively, if the arrangements are approved by a majority of nationalists and a majority of unionists, they would remain in place for eight years.
If the Northern Ireland Assembly voted to end the arrangements there would be a two-year notice period, during which the UK and the EU would have to agree ways to protect the peace process and avoid a hard border.
There is no fallback position in case the two sides cannot find a solution.
If a vote was not held – by choice or because the assembly was not sitting – then the government has committed to finding an “alternative process”.
Ex-PMs unite to oppose deal
Former prime ministers Sir John Major and Tony Blair appealed on Friday for MPs not to vote for the deal, claiming it would “wreck” the 1998 Good Friday peace agreement, which led to the end of the Troubles in Northern Ireland.
They called for another referendum on Brexit.
Sir John said the deal “splits Northern Ireland from the rest of the UK”.
Mr Blair said the Northern Ireland peace process could be “sacrificed on the Brexit altar”.
Former Northern Ireland first minister Lord Trimble, who won a Nobel Peace Prize for his role in Good Friday Agreement, backed the deal.
In a statement published by the Spectator, the former Ulster Unionist leader said it was a “great step forward” that was “fully in accordance with the spirit of the Good Friday Agreement”.
“What we now want to see is for the DUP and Sinn Féin to act together to bring the Good Friday Agreement back to life,” said the Tory peer.
“This is not the time to be looking for excuses not to implement either the Good Friday Agreement or the new deal.”