Telegram från AFP / Omni

Former British prime minister Tony Blair urged his Labour party on Wednesday to abandon "quasi-revolutionary socialism" as it seeks a new leader after its worst election defeat since the 1930s.

Britain's shellshocked left entered a period of soul-searching and mourning in the wake of last Thursday's drubbing at the polls.

The electorate handed Prime Minister Boris Johnson's Conservative party a clear mandate after he promised to take Britain out of the European Union on January 31.

But it also redrew the political map of England as swathes of its working-class north voted Conservative for the first time.

Labour's socialist leader Jeremy Corbyn -- a 70-year-old who campaign on a radical platform of state spending and re-nationalisation -- has since promised to step down.

The formal campaign to replace him is not set to begin until next month.

Yet several prominent Labour figures have already signalled their intention to enter a leadership contest.

Blair castigated Corbyn for "almost comic indecision" about which position to take on Britain's near half-century membership in the EU.

"The absence of leadership on what was obviously the biggest issue facing the country reinforced all the other doubts about Jeremy Corbyn," Blair said in a speech in London.

"Politically, people saw him as fundamentally opposing what Britain and Western countries stand for.

"He personified politically an idea, a brand of quasi-revolutionary socialism, mixing far-left economic policy with deep hostility to Western foreign policy, which never has appealed to traditional Labour voters."

Blair's popularity in Britain suffered from his decision to support the 2003 US invasion of Iraq on what proved to be false allegations that it had weapons of mass destruction.

Yet his 1997-2007 spell in office marked one of Labour's most electorally successful eras in its 119-year history.

He promoted centrist "New Labour" policies and embraced a leading role on the world stage that appealed to Britons during an era of economic growth.

Labour must now choose whether to adopt a similar ideology or push through with the leftist vision that Corbyn championed since taking charge in 2015.

Some potential successors said Corbyn had the right vision but the wrong approach.

"The case for a radical government has never been stronger," Labour's Brexit spokesman Keir Starmer told BBC radio.

He attributed the defeat to Labour's inability to counter Johnson's "get Brexit done" mantra with a clear case for why -- or whether -- Britain should still be a part of the EU.

"And we carried, I think, too much baggage into the election -- and anti-Semitism is the example of that," Starmer added.

The party was riddled with anti-Semitism scandals that saw several prominent members quit under Corbyn's watch.

Starmer is a London lawyer who had pushed for a second Brexit referendum and now appears to be trying to win over more leftist Labour votes.

Lawmaker Rebecca Long-Bailey -- a rising star who has faithfully defended Corbyn -- has emerged as the early favourite in a leadership race that is expected to feature several prominent women.

She has largely avoided the media since Friday's official results handed the Conservatives an 80-seat majority in the 650-member House of Commons.