The favourite to become the next Ukip leader has collapsed outside the European Parliament amid reports he was punched by a colleague.

Ukip said that Steven Woolfe collapsed outside the European Parliament following a "clear the air" meeting with colleagues this morning.

However party insiders told The Telegraph that Mr Woolfe was punched by a Ukip colleague following an altercation.

The Daily Telegraph understands that Mr Woolfe is suffering from bleeding of the brain after he was punched. One witness said he fell into a window after being punched.

Nigel Farage, who was reportedly present during the altercation, said: "I deeply regret that following an altercation that took place at a meeting of MEPs this morning that Steven Woolfe subsequently collapsed and was taken to hospital. His condition is serious."

Suzanne Evans, the party’s former deputy chairman and another possible future leader, Tweeted a message of support for her Ukip colleague.

Nigel Farage and Steven Woolfe credit: Daniel Leal-Olivas/PA

A UKIP spokesman said: Steven Woolfe MEP was taken suddenly ill in the European Parliament building in Strasbourg this morning. He has been taken to hospital in the city and he is undergoing tests."

Mr Woolfe announced he would stand after Ms James quit surprisingly on Tuesday evening after just 18 days as leader.

However he admitted that his decision only came after he had considered joining the Conservatives after becoming “enthused” by the start of Mrs May’s premiership.

Steven Woolfe credit: Brayan Lopez/REX/Shutterstock

Raheem Kassam, another contender for the leadership role, has cancelled his appearance on the BBC this afternoon in respect to Mr Woolfe.

Mr Woolfe – who is backed by Nigel Farage and the party’s biggest donor Arron Banks - said: “I have been enthused by the start to Theresa May's premiership.

“Her support of new grammar schools, her words on social mobility and the growing evidence that she is committed to a clean Brexit prompted me, as it did many of my friends and colleagues, to wonder whether our future was within her new Conservative Party.

The party’s ruling National Executive Committee meets on October 17 to discuss the latest crisis to hit the party and agree on the leadership time table to replace Mrs James.