Writing in The Mail on Sunday, the prime minister said Commons revolts by pro- and anti-EU Tories would undercut any chances of a deal with Brussels.
“My message to the country this weekend is simple: we need to keep our eyes on the prize,” May wrote. “If we don’t, we risk ending up with no Brexit at all.”
She urged MPs to take a “practical and pragmatic” approach or face a “damaging and disorderly” Brexit.
May admitted that some MPs were worried about her plan for a “common rule book” with the bloc for goods and customs traded within what she described as a new “UK-EU free trade area.”
However, May noted she had yet to see a “workable alternative” to the proposals, accepted by the cabinet at Chequers, that would enable trade to remain as “frictionless” as possible while preventing the return of a hard border between Northern Ireland and the Republic.
“We need to keep our eyes on the prize. If we don’t, we risk ending up with no Brexit at all,” she said.
“I know there are some who have concerns about the ‘common rule book’ for goods and the customs arrangements which we have proposed will underpin the new UK-EU free trade area. I understand those concerns,” the premier added.
“But the legacy of Brexit cannot be a hard border between Northern Ireland and Ireland that unpicks the historic Belfast Agreement,” she continued.
“It cannot be the breaking up of our precious United Kingdom with a border down the Irish Sea. And it cannot be the destruction of integrated supply chains and just-in-time processes on which jobs and livelihoods depend.”
Meanwhile the Trade Bill returns to the Commons on Tuesday with rival amendments tabled by pro- and anti-EU Conservatives.
May said some “wrecking” changes supported by members of the pro-Brexit Tory European Research Group would disrupt the government’s plans for a “no deal scenario.”
She said if this bill cannot pass, there will be “a damaging and disorderly Brexit” as “we would not be able to retain the benefits of more than 40 existing trade arrangements.”
“Neither will we have the means to protect consumers, industries and workers from being undercut by unfairly traded goods in a post-Brexit Britain,” she added.
Failure to reach a deal could imperil the EU’s budget, as well as the rights of EU citizens living in the UK.