British ministers agreed Tuesday to make no-deal Brexit planning "an operational priority" amid continued opposition to Prime Minister Theresa's May draft divorce deal, just 14 weeks before the country leaves the EU.

Following a meeting of her cabinet -- the last before parliament breaks for the Christmas/New Year break -- Defence Secretary Gavin Williamson said around 3,500 troops would be on stand-by to help deal with the "any contingencies" from a no-deal outcome.

But Brexit Secretary Steve Barclay said ministers still hoped to secure backing for May's agreement with the EU in a House of Commons vote delayed until next month.

He added that any responsible government would intensify preparations for the "default option" of leaving the European Union without a deal on March 29 next year.

"We agreed that preparing for no deal will be an operational priority within government," Barclay said. "But our overall priority remains to secure a deal."

He said departments would step up their advice to businesses on how best to prepare for the scenario, which many fear could be catastrophic for the British economy.

Businesses will be provided with a 100-plus page online preparation pack and emails will be sent to 80,000 of those most likely to be impacted over the next few days, according to Downing Street.