Will Boris Johnson make a comeback?

The UK will have a new prime minister by next week but who that person might be remains a big question mark so far.

Nobody has yet announced their intention to run for the Conservative Party leadership after Liz Truss resigned on Thursday, ending a turbulent 45 days in office.

Candidates to succeed Truss as the UK's prime minister have until 2pm (British time) on Monday to gather the support of 100 MPs to run.

This will be a fast-tracked contest unlike the one during the summer that saw Truss win the Conservative Party leadership to replace Boris Johnson. The new prime minister will be chosen by the end of next week, with the decision in the hands of Tory MPs and possibly Conservative Party members.

Former chancellor of the exchequer Rishi Sunak and Penny Mordaunt are being touted as possible contenders. Sunak lost in the run off against Truss among party members during the summer despite being the most popular among MPs. Mordaunt had also been a contender for the leadership.

But there is growing speculation that Boris Johnson may make a comeback with several MP backers tweeting ‘Bring Boris Back’. Johnson resigned in July following a series of scandals, some of which concerned parties he attended at a time when Britain was in lockdown.

The founder of ConservativeHome, is also a "real possibility", according to the founder of ConservativeHome, a right-wing blog which supports, but is independent of, the Conservative Party.

Contenders would need to have the support of 100 MPs and if more than two submit nominations, the person with the least support will drop out. An indicative vote will then be taken among MPs on the remaining two contenders, which may result in party members making the final decision through an online vote. If only one candidate submits a nomination that person will become the next prime minister.

Meanwhile, Labour leader Sir Keir Starmer and other opposition parties have called for an immediate general election.

Truss resigned on Thursday after a rebellion by Tory MPs, making her the UK's shortest-serving prime minister.

Truss faced six weeks of market turmoil that forced the resignation of her finance minister. A mini-budget that went for tax cuts spooked markets after doubts were raised on the sustainability of government finances at a time of hefty outlays to address the energy crisis.

Speaking outside Downing Street, Truss said she could not deliver the mandate on which she was elected by Tory Party members.