U.K. Prime Minister Boris Johnson and his governing Conservative Party are likely to capture a large parliamentary majority in the Dec. 12 elections that could decide the Brexit path next year and beyond, an exit poll showed.

The Conservatives were set to hold 368 seats in the 650-member House of Commons, up from a previous total of 298 before the elections, according to an exit poll commissioned by BBC News, ITV News and Sky News. The opposition Labour Party, led by Jeremy Corbyn, is projected to hold 191 seats, down from 243.

If the poll is correct, the Conservatives would have a majority of roughly 90 seats, their biggest since 1987, according to strategists at TD Securities. "A margin that large should be enough for [Johnson] to comfortably control the Parliamentary agenda over the coming five years," the strategists said.

The pound was trading more than 2% higher against the U.S. dollar shortly after 5 p.m. ET, minutes after the exit poll was released.

Securing an outright majority in Parliament means that Johnson would not need to form a coalition government with minority parties or strike a confidence-and-supply agreement with them. Johnson's government lost its working majority in September after a Conservative lawmaker switched parties.

In contrast, a hung parliament could leave the Conservatives struggling to find a feasible coalition partner, according to Kallum Pickering, senior economist at Berenberg. That could lead to another election, unless Labour could form a coalition with the Scottish National Party and Liberal Democrats, Pickering said.

Johnson became prime minister in July following the resignation of Theresa May, who failed three times to get her Brexit deal through Parliament. In October, Johnson called for a snap election to break the Brexit deadlock, as the EU moved the Oct. 31 Brexit deadline to Jan. 31, 2020. He vowed to get Brexit done in January if he wins a majority in the elections.

The U.K. House of Commons in October approved on second reading the revised Withdrawal Agreement Bill negotiated by Johnson. That was the first time that Parliament has voted in favor of a Brexit deal since a referendum to leave the EU in June 2016.

"Let's not go back to the broken Parliament we had before this election was called," Johnson wrote on Twitter before the polls closed. "Let's move forward with a majority Conservative government that can get things done."

In the 2017 elections, the Conservatives emerged as the largest party, as correctly predicted by an exit poll, but lost their parliamentary majority. An exit poll after the 2015 elections failed to predict a Conservative majority.