A Tory MP who quit as foreign minister instead of serving in a Boris Johnson government has called for an emergency vote to test the likely winner’s majority in parliament.

Sir Alan Duncan, who resigned as foreign office minister on Monday, immediately asked speaker John Bercow to call a debate.

The emergency debate would have asked MPs to consider whether the Commons “supports the [next PM’s] wish to form a government”. 

The move could have squashed Johnson’s premiership before it began as it would have effectively acted as a confidence vote and have taken place before the next PM requested the Queen’s formal backing to take charge. 

It is understood Bercow has refused the request. 

It comes ahead of Johnson’s widely anticipated victory in the Tory leadership race over rival Jeremy Hunt on Tuesday. 

Duncan told the BBC he quit government to push for the debate, which could have triggered a crisis for the UK’s next premier before he reached Number 10. 

Duncan is likely to be the first of many ministers to quit the rather than serve under Johnson’s leadership or be fired.

Chancellor Philip Hammond and Justice Secretary David Gauke have both confirmed they will step down before Johnson becomes prime minister on Wednesday afternoon.

In his resignation letter, Duncan said: “It is tragic that just when we could have been the dominant intellectual and political force throughout Europe, and beyond, we have had to spend every day working beneath the dark cloud of Brexit.”

Duncan, a university friend of May, praised the “faultless dignity and an unstinting sense of duty” she had shown.

“I am only sorry that your three years as prime minister have been brought to an end,” he said.