Boris Johnson says there is a “strong possibility” the UK will fail to strike a post-Brexit trade deal with the EU.
Speaking for the first time since a crunch meeting in Brussels, the PM said “now is the time” for firms and people to prepare for a no deal outcome.
Talks continue between the two sides but Mr Johnson said they were “not yet there at all” in securing a deal.
Time is running out to reach an agreement before the UK stops following EU trade rules on 31 December.
Weeks of intensive talks between officials have failed to overcome obstacles in key areas, including competition rules and fishing rights.
Mr Johnson met European Commission President Ursula von der Leyen on Wednesday, but the pair failed to make a breakthrough.
Mr Johnson pledged British negotiators, who earlier resumed talks with their EU counterparts in Brussels, would “go the extra mile” to reach a deal.
But he said the EU wanted to keep the UK “locked” into its legal system, or face punishments such as taxes on imports, which had “made things much more difficult”.
The PM added that the EU’s proposals would mean, despite leaving the bloc earlier this year, the UK would be forced to remain a “twin” of the 27-country organisation.
“At the moment, I have to tell you in all candour, the treaty is not there yet and that was the strong view of our cabinet,” he said.