The North West MEP Paul Nuttall is resigning from UKIP over the party's association with far right extremist Tommy Robinson.
Mr Nuttall, a former UKIP leader who represents the North west of England in the European Parliament has this morning announced his resignation from the party.
He will continue to be an MEP until his term expires in 2019.
His resignation was prompted by the controversial decision to hire former English Defence League leader Robinson - whose real name is Stephen Yaxley-Lennon - as UKIP's adviser on rape gangs and prison reform.
Mr Nuttall said: "After much soul-searching over the past week, I have concluded that I must, as of today, resign as a member of UKIP. I do this with an immense amount of reluctance and regret, as I have worked tirelessly for the party for the past fourteen years.
"I am resigning because the party is being taken in a direction which I believe is harmful to Brexit. The association with Tommy Robinson will simply appal many moderate Brexit voters and inevitably be detrimental to the cause.
"The Tommy Robinson issue should have been shelved and debated within the party following Brexit; in line with the sensible decision taken by the National Executive Committee last month. The party leadership and my MEP colleagues have been aware of my views on this issue for some time.
"Putting Tommy Robinson front and centre, whilst Brexit is in the process of being betrayed is, in my view, a catastrophic error.
"To conflate Brexit and Robinson at this crucial moment is to put the Eurosceptic cause in danger and I cannot and will not be party to that."
Nigel Farage, another former UKIP leader, has also announced he is leaving the party over the association with Tommy Robinson.