The investigation into the clash between two Ukip MEPs which left leadership frontrunner Steven Woolfe in need of hospital treatment may struggle to get the bottom of what happened, the party's chairman has admitted.

Paul Oakden said there were no independent witnesses to the altercation at the European Parliament in Strasbourg on Thursday between Mr Woolfe and Mike Hookem.

With Mr Woolfe now recovering, Mr Oakden said he was "hopeful" the two men would accept that what had happened was "regrettable" and agree to "move on" and get on with the election of a new party leader.

The confrontation erupted during a heated meeting of Ukip MEPs. Two hours later Mr Woolfe collapsed and was rushed to hospital, where he underwent a brain scan.

Mr Woolfe told the Daily Mail that Mr Hookem "came at me and landed a blow" after they left the meeting room to continue the argument and he banged into a door frame.

Mr Hookem, however, has said he did not punch Mr Woolfe and that he did not see him hit his head.

Mr Oakden, who is leading the investigation into what happened, said the conflicting accounts may make it difficult to establish the truth.

"I have spoken to people who were there and everything I am being told at the moment would suggest that there were no witnesses. That is going to present a problem," he told BBC Breakfast.

"I hope that we don't end up in a situation where we just have two members here disagreeing on the facts but with nobody else able to corroborate either.

Paul Oakden