UK prime minister Boris Johnson could be impeached and removed from office if he tries to force through Brexit.

Johnson has insisted that he will refuse to delay Brexit despite members of parliament passing a law compelling him to seek a delay.

Under an arcane parliamentary procedure members of parliament can be charged with "high crimes and misdemeanors."

The procedure was last used in 1806 and was considered obsolete.

However, Johnson himself previously called for it to be used against former Prime Minister Tony Blair.

Visit Business Insider's homepage for more stories.

Boris Johnson could be impeached and removed from office if he attempts to take Britain out of the EU without a deal, under plans being pushed by an opposition leader.

The prime minister has insisted that he will refuse to delay Brexit, despite members of parliament passing legislation this week that will compel him to request a three month extension from the EU.

A spokesperson for Johnson said on Monday that "the government will not be asking for an extension."

Plaid Cymru's Westminster leader, Liz Saville Roberts said that MPs should use the arcane procedure of impeachment if Johnson continues to refuse to seek a delay.

"No one is above the law, Boris Johnson shouldn't risk finding that out the hard way," she said.

Read more: Boris Johnson could soon be forced to resign as prime minister and make way for Jeremy Corbyn

The threat came after the former Director of Public Prosecutions said Johnson could be sent to prison if he refuses to comply with the law.

Lord MacDonald said that refusal to comply with the legislation would be an offence under the law that may require jail time.

"A refusal in the face of that would amount to contempt of court which could find that person in prison," Lord MacDonald said on Sunday.

No prime minister has ever been impeached in the UK. However, under the procedure, which was last used in 1806, any member of parliament can be tried by their peers for "high crimes and misdemeanors, beyond the reach of the law or which no other authority in the state will prosecute."

Johnson himself previously advocated using it against former prime minister Tony Blair.

In a column headlined "Isn't it time we impeach Blair over Iraq," Johnson argued that "the procedure would at least force Blair to come clean, and say why he felt it necessary to be so reckless with the truth."

Saville Roberts said the same argument could be made against the current prime minister.

"If the prime minister becomes a law-breaker, we have an even stronger case for impeachment than the very cause he advocated back in 2004," she said.

Johnson has reportedly told colleagues that he would not break the law. However, the foreign secretary Dominic Raab on Sunday said the government planned to "test" the law to its limit.

Under one plan reportedly being considered by Downing Street, the UK would request an extension but also send a second letter suggesting that they did not want one.

The former Labour Lord Chancellor Lord Falconer tweeted on Sunday that this plan would "destroy [the] statutory purpose" of the bill and therefore break the law.