Nigel Farage has hinted at becoming leader of the Brexit Party after it was officially approved.
The Eurosceptic party was formally recognised by the Electoral Commission on 5 February, allowing it to field candidates at upcoming elections.
The former UKIP leader said he would stand as a candidate for the new party in May’s European Parliament elections if Brexit is delayed.
He said the party, which publicly launched on 20 January, “has my absolutely full support”.
The UK is scheduled to leave the European Union on 29 March but Mr Farage said that if MPs “kick the can down the road” by extending Article 50, “then logically we would have to fight European elections and I would certainly stand in them in those circumstances”.
The registration of the Brexit Party should be a warning to MPs considering backing any effort to extend Article 50 in order to allow more time for negotiations, he said.
MPs considering such a move “need to be aware there could be a very serious electoral threat to them”.
Former UKIP economic spokesperson, Catherine Blaiklock, who founded the party, told the Daily Telegraph that a “number of hundred” Conservative members wanted to defect the new party and the figure was likely to rise.
However Mr Farage said the party would gain support from across the political spectrum as people are increasingly identifying along Leave and Remain lines rather than as Conservative or Labour.
He said: “If the need comes for the Brexit Party to be mobilised, I think it will draw support from across the entire spectrum.
“I genuinely believe people would be very surprised at the support it would attract.”
He added: “There is a live vehicle there from which to fight back.
“There are many millions of people out there at the moment feeling disenfranchised completely, feeling that they are more Leavers, or Remainers, but feeling they are more Leavers than they are Labour or Tory supporters and this would give them a focus.”
Mr Farage, who is also vice-chairman of the pro-Brexit organisation Leave Means Leave, resigned from UKIP over the appointment of Tommy Robinson as an adviser to party leader Gerard Batten.