Cumbrian MEP Steven Woolfe has announced he is quitting Ukip.
He has also said he has made a police complaint about the altercation with a fellow MEP which left him in hospital.
Woolfe was under pressure to abandon his Ukip leadership bid following his altercation with fellow MEP Mike Hookem which left Woolfe in hospital.
Senior party figures suggested Mr Woolfe's apparent willingness to resort to violence rendered him unfit for leadership.
Mr Woolfe was left with a suspected bleed on the brain after allegedly being punched during a heated Ukip row earlier this month in the European Parliament building in Strasbourg.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here