Any attempt to shut down parliament to force through a no-deal exit from the EU could kill off Brexit completely, Tory leadership hopeful Matt Hancock has warned.

In an open letter to an unnamed “colleague”, the health secretary slammed the idea as “neither serious nor credible”.

It comes the day after Dominic Raab – who is also vying to replace Theresa May in Number 10 – suggested he could “prorogue” the Commons in order to stop MPs from forcing the government to further delay Brexit.

“To suspend parliament explicitly to pursue a course of action against its wishes is not a serious policy of a prime minister in the 21st century,” Hancock wrote.

He said the move could lead to an “instant” no-confidence vote in parliament, meaning the new PM would risk “barely having time to sit at their desk in Downing Street before being removed from office”.

“The most likely outcome would be a general election, risking Corbyn by Christmas, a second referendum and killing Brexit altogether.”

Raab has already faced widespread criticism for his comments, with leadership contender Rory Stewart suggesting that an attempt to shut down parliament could be “illegal”.

“It would be unconstitutional. It would be undemocratic. And it wouldn’t work,” he told ITV.

Meanwhile, Commons speaker John Bercow warned Raab he would not allow him to close down parliament.

Speaking to MPs on Thursday morning, Bercow said: “Parliament will not be evacuated from the centre stage of the decision making process on this important matter.

“That simply us not going not happen it’s just so blindly obvious.”

The row comes ahead of the Tory leadership contest starting in full on Monday, with May set to resign tomorrow. There are currently 11 contenders for the top job, with Kit Malthouse and Brexit minister James Cleverly having already pulled out.