The former leader of Ukip Paul Nuttall has quit the party over its decision to appoint Tommy Robinson as an adviser.
This came as Ukip's leader in Scotland, MEP David Coburn, also resigned in protest at the "English nationalist direction" adopted by the party.
They form a list of high-profile members to recently leave Ukip along with Nigel Farage, who quit earlier this week.
The 36-year-old former leader of the English Defence League Mr Robinson, real name Stephen Yaxley-Lennon, was given the role to support current UKIP leader Gerard Batten in November.
In a statement regarding his resignation, Mr Nuttall, the MEP for North West England, 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."
He then went on to explain his reasoning and said: "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.
"I will continue to serve the North West of England in the European Parliament until my term expires."
In a letter to Ukip's party chairman, Mr Coburn accused the party of promoting anti-Islamic policies and English nationalism.
In the message, also sent to the chair of the party in Scotland, Mr Coburn said: "As a unionist, I abhor English nationalism as much as I abhor Scottish nationalism.
"The party has been infiltrated by people with an alternative agenda, which is not the one on which I stood when I was elected and sadly does not represent the values for which Ukip once stood.
Nigel Farage, who had three different stints as Ukip leader, cited Mr Robinson as an issue when he quit.
He said: "Over the course of the last few months, under this leader, he seems to be pretty obsessed with Islam. Ukip wasn't founded to be a party based on fighting a religious crusade.
"He's also obsessed with this figure called Tommy Robinson, who is seen by some to be a great hero standing up and fighting for working class people, but who has a pretty suspect record."
