'I will fight it with everything I've got': Defiant Theresa May vows to contest TONIGHT'S no-confidence vote after Tory rebels trigger leadership battle by finally getting 48 letters from MPs.

Theresa May vowed to fight with 'everything I've got' today after a Tory no-confidence vote was dramatically triggered - and will be held tonight. The PM said she would not give up after Eurosceptics [anti-European Union] secured the 48 letters from MPs needed to force a ballot that could end the PM's time as leader. Sir Graham Brady, the chair of the powerful 1922 committee, said the threshold had been 'exceeded' and Mrs May was eager to resolve the issue 'rapidly'. He said she will deliver a speech to MPs at 5pm before voting begins an hour later. She was very concerned that the matter should be resolved as rapidly as possible.' Cabinet ministers immediately rallied to try and shore up support for Mrs May, warning that 'chaos' will ensue if the party kicks her out at this point. Mrs May wins tonight and said Brexit will have to be postponed, probably six months, if she loses. 'Clearly there would have to be a delay,' he said. If she wins by one vote she is immune from challenge for 12 months but narrow victory could still be fatal If Mrs May loses she will stay on as Prime Minister while another Conservative Party leader is chosen.In a defiant speech on the steps of Downing Street, Mrs. May warned Brexit would need to be delayed beyond March 29 if she loses and Labor leader Jeremy Corbyn might end up in power.  Mrs May was forced to postpone a crunch Commons Brexit vote to avoid humiliating defeat.A leadership contest will throw Brexit as well as the Tories into turmoil. Mrs May decided earlier this week not to put her deal to a vote, accepting it would be heavily defeated.She announced she would try to secure fresh concessions on the Irish border backstop, and would hold a fresh parliamentary vote by January 21. A challenge would throw that calendar into chaos.

Mrs May can stay on if she wins the confidence ballot by just one vote, and would theoretically be immune from challenge for another 12 months. But in reality anything short of a handsome victory will make it almost impossible for her to cling on.

How can Theresa May be ousted as Tory leader?

A Tory leadership contest can be called in one of two ways - if the leader resigns or if MPs force and win a vote of no confidence in them.

It is not the same as a vote of confidence in the government - which happens on the floor of the Commons and involves all MPs. 

Calling votes of no confidence is the responsibility of the chairman of the 1922 Committee, which includes all backbench Conservative MPs.

Chairman Graham Brady is obliged to call a vote if 15 per cent of Tory MPs write to him calling for one - currently 48 MPs. 

The process is secret and only Mr Brady knows how many letters he has received.

Once triggered, the ballot can be organised very quickly - potentially even the next day.

The no-confidence vote is purely on whether the leader should stay in place or not, rather than a contest.

Crucially, if the incumbent receives more votes in support than opposed they cannot be challenged for 12 months.

The procedure was last used in 2003 when Iain Duncan Smith was removed as Tory leader.

If the leader is ousted, they typically remain as Prime Minister until a successor is appointed and ready to be confirmed by the Queen.

Any MP - apart from the ousted leader - is eligible to stand in the subsequent contest.

Conservative MPs hold a series of ballots to whittle the list of contenders down to two, with the lowest placed candidate dropping out in each round.

The final two candidates are then offered to the Tory membership at large for an election.