British Prime Minister Boris Johnson said on Sunday his failure to deliver Brexit last week as he had promised was a “matter of deep regret”, but his deal remained the only way to get Britain out of the bloc.

Johnson had previously pledged to take Britain out of the European Union (EU) with or without a deal on October 31, before lawmakers voted to force him to seek an extension until January 31.

The leader of Britain’s Liberal Democrats Jo Swinson told Sky News that Johnson “only had himself to blame” for the failure to deliver, saying his “do or die” pledge never should have been made.

In Britain’s tortuous journey since the 2016 referendum vote to leave the EU, businesses and economists have cautioned that leaving the bloc without a deal to smooth the transition would hurt the British economy. Proponents of a no-deal Brexit say it provides a clean break from EU rules and regulations.

Johnson’s Conservative Party has an eight percentage-point lead over the opposition Labour Party, an ORB poll for the Sunday Telegraph showed, ahead of an election on December 12.