Dr Sarah Wollaston has urged the public to "bear with" Change UK - The Independent Group, after three people left the party in quick succession.
Joseph Russo and Ali Sadjay were dropped as EU election candidates after incriminating social media posts came to light, and yesterday, Change UK activist Dan Heley quit the party, claiming it was "riddled with distrust".
Appearing on the breakfast show, Dr Wollaston defended the party's choice of candidates, insisting they had "taken action immediately" when the offensive tweets emerged.
"We did go to the trouble of actually trying to do vetting on the candidates," she told talkRADIO's Julia Hartley-Brewer.
"The difference between us and perhaps others, is that we have taken action immediately when that has come to our attention."
She continued: "This was an election that nobody was expecting to hold, where people have had to find candidates in a much more rapid process than anyone would have wanted to have done in an ideal world."
One of the tweets by Mr Russo, who was the lead MEP candidate for Scotland, reportedly read: "Black women scare me. I put this down to be chased through Amsterdam by a crazy black wh*re."
And Mr Sadjay was accused of "hate speech" over his tweet, about "Romanian" pickpockets.
"One thing we all know is that when you're a small emerging party you're going to have these issues," Dr Wollaston added.