A leading British Conservative has defected to the Remain camp, citing Nigel Farage's controversial anti-migrant poster as the final straw.
Baroness Warsi, a former Foreign Office minister, had been a Brexit supporter but said she had been turned off by what she described as their spreading of "hate and xenophobia".
The UKIP poster she said was the final straw showed non-white migrants queuing to get into Europe under the slogan "Breaking Point".
She said: "That 'breaking point' poster really was, for me, the breaking point to say: 'I can't go on supporting this'.
"Are we prepared to tell lies, to spread hate and xenophobia just to win a campaign? For me, that's a step too far."
But Bernard Jenkin, a senior figure in the Leave camp, tweeted that he had not seen Baroness Warsi at a single meeting - suggesting she was not part of the campaign.
I helped set up @vote_leave and she has not been at a single meeting I have attended. "defects" just not accurate! https://t.co/hnaoXv9y5T
— Bernard Jenkin (@bernardjenkin) June 19, 2016
She is not the first politician to criticise the poster.
Scotland's First Minister Nicola Sturgeon described it as "vile and racist", while Chancellor George Osborne said it was "disgusting" and had "echoes of literature used in the 1930s".
Campaigners on the Leave side were equally as scathing, with Justice Secretary Michael Gove saying he "shuddered" when he saw the poster and Chris Grayling calling it "wrong".
UKIP leader Mr Farage defended the poster, however, telling Sky News that it "reflects the truth" about migration and the European Union.
Mr Farage told Sky News that the poster - which has been reported to police for alleged racism - would not be appearing again as it was the first in a series of five planned for the referendum campaign's final days.
He said the campaign would not have attracted so much attention had it not been for the murder of Labour MP Jo Cox hours after the poster was launched last Thursday.
Baroness Warsi is accusing some Brexit campaigners of spreading "hate and xenophobia" | Photo: PA Images
Farage said: "That poster reflects the truth of what's going on. There's a new poster coming out tomorrow morning.
"I wish an innocent Member of Parliament had not been gunned down in the street and frankly, had that not happened, I don't think we'd have had the kind of row we have had."
Mr Farage risked a row with his fellow Leave campaigners as he responded to criticism from Mr Gove.
He said: "Michael Gove better take a look at his own posters - pictures of Abu Hamza, warnings about terrorists and murderers coming into Britain at free will."
Remain-supporting Labour leader Jeremy Corbyn meanwhile told the BBC's Andrew Marr that limiting immigration would be impossible under EU rules.
Asked if an upper limit could be put on the numbers of EU immigrants to the UK, he said: "I don’t think you can have one while you have free movement of labour.
"The very principle of a single market across Europe is the free movement of people."
