Theresa May is fighting to keep the delicate Brexit negotiations on track after the DUP threatened to vote down the budget and bring down her premiership if a divorce deal meant that Northern Ireland was treated separately from the rest of the UK.
The prime minister responded by summoning senior cabinet members to Downing Street on Thursday, where she was expected to update them on progress amid signs that the sabre-rattling DUP and the Tory right were acting in concert against her.
Ministers are expecting to hear more about the status of the withdrawal agreement – which includes the Irish border backstop – although its text is deemed so sensitive that it is not expected to emerge until European leaders meet next week.
A few hours later, DUP leader Arlene Foster, in Brussels for talks with EU officials, said that she had “been telling people about our red line” and added: “We can’t have a customs or regulatory barrier in the Irish Sea because that would cause us to be a rule-taker from Europe.”
The DUP threat comes days after the hard-Brexit ERG indicated that its MPs – thought realistically to amount to around 40 – would also be prepared to vote against the budget a few days after it is delivered by Philip Hammond on October 29.
Downing Street insisted that a defeat on the budget would not amount itself to a vote of no confidence under the terms of the fixed term parliament act, but in reality failing to pass a finance bill would amount to a humiliation for Theresa May, and put her position as prime minister in jeopardy.