BORIS JOHNSON

The likely months-long campaign, potentially pitting more than a dozen Conservative MPs and multiple factions of the ruling party against each another, is set to be formalised Monday.

The early favourite is former finance minister Rishi Sunak, who launched his campaign Friday after helping to kickstart the cabinet revolt that led to Johnson's forced resignation

The contest to replace British Prime Minister Boris Johnson gathered pace on Sunday as five more candidates declared their intention to run, with many pledging lower taxes and a clean start from Johnson's scandal-ridden premiership.

UK political resignations: the current uncertainty could affect the economy for nearly two years

Item A on next British PM's agenda: inflation crisis

Ukrainian President Volodymyr Zelensky called Johnson to express his "sadness" over his resignation.

Russian politicians lined up to celebrate the downfall of Boris Johnson on Thursday, casting the British leader as a "stupid clown" who had finally got his just reward for arming Ukraine against Russia.

While the European Commission publicly dodged commenting about the political upheaval in the UK, others in Brussels' orbit let loose.

The resignation of Prime Minister Boris Johnson deepens the uncertainty hanging over Britain's economy, already under strain from an inflation rate heading for double digits, the risk of a recession and Brexit.

Alexander Boris de Pfeffel Johnson had a conventional rise to power for a Conservative politician: first the elite Eton College, then Oxford University.

Britain faces an unsustainable debt burden more than three times its current level unless future governments raise taxes to fund increasing costs from an ageing population and falling revenue from taxation on motor fuel, a watchdog warned on Thursday.

Former British Prime Minister John Major said Boris Johnson should be replaced immediately rather than be allowed to remain as a caretaker leader because his cabinet may struggle to "restrain him", amid wider calls for him to be removed now.

Boris Johnson will announce his resignation as British Prime Minister on Thursday, a government source said, after he was abandoned by ministers and his Conservative Party's lawmakers who said he was no longer fit to govern.

Within a little over 24 hours, 43 ministers and their Tory MP aides had quit, mostly from more junior positions outside the cabinet, while Gove was sacked.

British Prime Minister Boris Johnson was clinging to power on Wednesday, after ministers quit the cabinet following a scandal over whether Johnson's office told the truth about sexual harassment allegations against a lawmaker.

Britain's new finance minister Nadhim Zahawi pledged on Wednesday to rebuild and grow the struggling economy and said he would look at all policy options, including possible tax cuts.

British markets braced for more political uncertainty on Wednesday, with investors keen to see if the new finance minister loosens the purse strings and wondering whether Prime Minister Boris Johnson will survive an exodus of support.

Sterling slumped against to a two-year low against the dollar on Tuesday as a crisis in British Prime Minister Boris Johnson's government compounded pressure on a currency already reeling from recession fears and a resurgent greenback.

Britain's finance and health ministers resigned in quick succession on Tuesday, in moves that put the future of Prime Minister Boris Johnson in peril after a series of scandals that have damaged his administration.

The resignations -- after a succession of crises that led to a vote of confidence in Johnson's leadership -- did nothing to dampen speculation that both men still have an eye on the top job.

Britain's new finance minister Nadhim Zahawi takes the reins of an economy struggling under the strain of nearly double-digit inflation and a slowdown that looks set to be more severe than in most of the world's other big nations.