Prime Minister Boris Johnson and Leader of the Labour Party Jeremy Corbyn shake hands during the ITV Leaders Debate on November 19, 2019 in Salford, England.

The British electorate faces a "terrible choice" at the ballot box next month, according to the chief economist at Pantheon Macroeconomics.

His comments come shortly after the leaders of Britain's two biggest political parties clashed in their first televised debate of the election campaign on Tuesday evening.

Prime Minister Boris Johnson vowed to end ongoing "national misery" by delivering Brexit by the end of January.

The Conservative Party leader, who had previously promised to deliver Brexit "do or die, come what may" by the end of October, sought to reinforce a pledge that his party would be able to resolve the Brexit crisis quickly, saying his government had a divorce deal that is "oven-ready."

In contrast, Jeremy Corbyn, leader of the opposition Labour party, said he would "get Brexit sorted by giving you, the people, the final say."

Labour wants to negotiate a new deal with the European Union, with a customs union and a closer relationship with the single market. Corbyn has said this deal would be put to a public vote, with citizens choosing either to leave on Labour's terms or to remain.

Corbyn, who was asked nine times by Johnson to say whether his party would then campaign to stay in the bloc or leave, said he would respect the decision of the people.