Opponents of Britain's prime minister, Theresa May, mounted a challenge against her leadership of the Conservative Party on Wednesday, a move that culminated in a secret-ballot of the party's members of Parliament later in the evening.

May said ahead of the challenge from within her own party – a so-called vote of no confidence – that the issue was a distraction that could end up "delaying or even stopping Brexit" and insisted she would "contest that vote with everything I have got".

She had been under pressure for months over her handling of negotiations with the European Union about the Unite Kingdom's pending exit from the bloc at the end of March.

She said changing party leader, and therefore prime minister, would "put our country's future at risk and create uncertainty when we can least afford it".

She has been criticized from all sides, with some Conservative MPs favoring a harder line with the EU, others favoring a softer line,and some hoping to backtrack and remain an EU member.

Wednesday's challenge was triggered when the influential 1922 Committee that oversees party rules received the requisite 48 letters from Conservative Party MPs calling for a leadership vote.

The party has 315 MPs and May needed the support of at least 158 to hang onto her job.

If she survived Wednesday night's vote, party rules would prevent the maverick MPs wanting to unseat her from mounting another challenge for at least a year.

The BBC's political editor, Laura Kuenssberg, said the vote, no matter what the outcome was likely to slow down Brexit deliberations.

Owen Paterson, one of the Conservative MPs who submitted a letter to trigger the leadership challenge, told the BBC: "She is sadly determined to stick to her deal which is not going to get through the House of Commons, and worse, if it did get through the House of Commons, she would lose the support of the DUP, which triggers a general election."

May has been prime minister since 2016,when she took the reins in the aftermath of the UK's referendum decision to leave the EU.

If she lost in Wednesday night's vote, she would not be allowed to stand in the leadership battle that would follow and likely last six weeks.

In the hours before the leadership vote, more than 110 Tory MPs had gone on record saying they would support May in the challenge.

So far, none of Theresa May's critics have publicly stated they want to replace her as leader of the Conservative Party but several MPs do seem to be in the frame.

Challengers taking part in any leadership battle are thinned out during a series of votes that involve Conservative MPs, until only two remain.

The winner is picked from the last two in a nationwide poll of rank-and-file Conservative Party members.

Justice Secretary David Gauke told Radio 4's Today program a leadership tussle could rumble on until late January or February.

Those being talked about as potential leaders include:

Boris Johnson. The prominent Brexiteer and former foreign secretary who was once mayor of London is the bookies' joint-favorite. He has been a huge critic of May and her proposed Brexit deal. Educated at Eton, colorful and flamboyant, he has been frequently tipped as a future leader.

Dominic Raab. The former Brexit secretary who resigned after disagreeing with May's post-Brexit vision is the joint-favorite among bookmakers, alongside Johnson. The son of an emigrant from Czech Republic, he is a prominent Brexiteer who wants an arms-length relationship with the EU.

Sajid Javid, Britain's home secretary, has consistently supported May but could step in if she is unseated as party leader. Like May, Javid wanted the UK to remain in the EU ahead of the referendum. He has been home secretary since April and is the first person from a visible ethnic minority to hold the position.

Michael Gove. Despite saying it is "extremely unlikely" he would stand in any leadership campaign, he has frequently been mentioned as a possible future party leader. The former journalist has held senior positions in government and is believed to be very ambitious.