Former finance minister Rishi Sunak has won the biggest backing from Conservative MPs in the first vote to choose who will succeed Boris Johnson as party leader and UK prime minister while two more rivals were eliminated.

Sunak, whose resignation as finance minister last week helped precipitate Johnson’s fall, secured support from 88 of the party’s 358 MPs, with junior trade minister Penny Mordaunt second with 67 votes and foreign minister Liz Truss third with 50.

Former equalities minister Kemi Badenoch received 40 votes, Tom Tugendhat, chair of parliament’s Foreign Affairs Committee, received 37 and Attorney General Suella Braverman received 32.

The six candidates will go through to a second round on Thursday.

Nadhim Zahawi, who took over as finance minister from Sunak last week, and former foreign minister Jeremy Hunt were knocked out on Wednesday after failing to get the required minimum of 30 votes. 

They join three other contenders who dropped out the day before.

Subsequent ballots will be held among the Conservative MPs, eliminating the candidate with the fewest votes each time, to whittle the field down to a final two by July 21. 

The new leader will then be chosen from those two by the 200,000 Conservative party members in the country at large and be announced on September 5.

While Sunak might be the most popular contender with his colleagues, a YouGov poll of nearly 900 party members found Mordaunt was the favourite, beating any of the others in a run-off. 

She had a huge lead over Sunak, who fared badly against almost all his rivals, and is now the bookmakers’ favourite.

Whoever wins will face a daunting in-tray while having to rebuild public trust bruised by a series of scandals involving Johnson, from the breaking of COVID-19 lockdown rules to appointing an MP to government despite having been told of allegations of sexual misconduct.

The United Kingdom’s economy is facing rocketing inflation, high debt and low growth, leaving people grappling with the tightest squeeze on their finances in decades. 

All this is set against the backdrop of an energy crunch exacerbated by the war in Ukraine, which has sent fuel prices soaring.

As the contest intensifies it has also become increasingly fractious as rival camps trade barbs and some offer a series of eye-catching tax cutting pledges.

Sunak said it was not credible to offer more spending and lower taxes, saying he was offering honesty “not fairytales”.

Zahawi said he had been smeared over his personal finances while culture minister Nadine Dorries, who was fiercely loyal to Johnson and is now backing Truss, has accused Sunak’s team of “dirty tricks” as part of a “Stop Liz” strategy.

“I believe his (Sunak’s) behaviour towards Boris Johnson, his disloyalty means that I could not possibly support him,” minister for Brexit opportunities Jacob Rees-Mogg told Sky News on Wednesday.

Johnson, who won a large majority in December 2019, announced last week that he would step down after a torrent of resignations from ministers and with many Conservative Party MPs in open revolt.