Medical examinations suggest Steven Woolfe has bruising on his face not consistent with just a fall or seizure, the Ukip MEP has revealed.
The news will intensify controversy that has engulfed Ukip since Woolfe was taken to hospital after an "altercation" with fellow MEP Mike Hookem.
A spokesman for Woolfe said: "A team of experts independent of the hospital staff were called in to examine physical injuries to Steven's face, head and body that were inconsistent with just a seizure, or a fall as a result of a seizure.
"The team of experts also examined other pieces of evidence including clothing and images relating to those injuries.
"Their report will shine a different light on claims currently being made in the media."
Hookem has insisted he did not punch Woolfe, and the incident amounted to "handbags at dawn".
A spokesman for the Yorkshire and North Lincolnshire MEP said: "Mr Hookem stands by the statements that he made in various media interview yesterday regarding Steve Woolfe.
"Mr Hookem will now be seeking legal advice in relation to Woolfe's allegations and will be making no further comment at this time."
Earlier, Hookem insisted claims he punched Woolfe were untrue. He said: "That's totally wrong. I never touched him, never hit him, never punched him, never slapped him or anything else I've been accused of doing."
After a disagreement over the reasons for Woolfe being barred from the last leadership contest, Hookem said his colleague told him: "Well if that's the tone of this meeting, maybe me and you should take it outside the room, mano-a-mano."
He said Woolfe then picked up his jacket and went out of the room.
"So I went out of the room into this small anteroom where he came at me. And what occurred was a tussle. Nothing happened. It was literally seconds because the other MEPs followed us in there.
"The door opened. I backed off. Steven fell through the door and I went back to sit back down again."
His account is at odds with North West England MEP Woolfe, who told the Daily Mail Hookem "came at me and landed a blow" and that he fell back and hit the door frame.
The latest twist to the saga came as MEP Roger Helmer said a "black mark" will be put over Woolfe's standing for the leadership of Ukip if a party probe rules he intentionally started a fight.
Helmer insisted questions would be raised over Woolfe's fitness for the party's top job if it is found he instigated the "altercation" with Hookem.
The intervention came after senior party figures suggested Woolfe's apparent willingness to resort to violence made him unsuitable for leadership.
Helmer said an internal Ukip investigation into the tussle between the two MEPs would be crucial to Woolfe's future in the party.
"If it's concluded that he started, he intentionally started, a fight - if, I stress, if - then that would be a black mark against his ability to stand.
"I think as a conclusion of that investigation the party will consider whether disciplinary measures are appropriate and that might have implications for Steven Woolfe's candidacy," the East Midlands MEP told BBC Radio Four's Today programme.
European Parliament president Martin Schultz announced that he was launching an investigation into the conduct of the two MEPs, which could see them suspended from voting and their expenses cut.
In response to Woolfe's injury claims, Hookem has released a photograph of his hands which he says display no bruises, cuts, or grazes, to back up his insistence that he did not punch his fellow MEP.
Hookem told Sky News he posted the photograph online with a picture of Woolfe in his hospital bed to back his version of events.
"I am now disputing everything Steven Woolfe is saying.
"That photograph shows my hands, it was the day after the altercation, supposed altercation, to show that there is no marks whatsoever, it's high definition, there is no marks whatsoever on my hands.
"And the photograph of Steven Woolfe sitting in a hospital bed where there is no marks whatsoever on his face.
"It is playground behaviour and I have apologised to the membership, and I've apologised to the party.
"It shouldn't have happened, it was silly. And I am quite prepared to put my hands up to say it's silly, we shouldn't have done it, let's shake hands, let's move on."