A senior Conservative has switched from supporting Leave to Remain, accusing some Brexit campaigners of spreading "hate and xenophobia".
Baroness Warsi, a former Foreign Office minister, said the final straw was a Ukip poster showing migrants queuing up to get into Europe under the slogan "Breaking Point".
Lady Warsi told The Times: "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."
Lady Warsi resigned from the Government in 2014, saying she could not support its position on the conflict in Gaza.