UKIP has accused the Conservative party of running a "morally reprehensible" smear campaign by trawling through potential councillors' Twitter and Facebook posts.
The party - which is investigating a handful of candidates over links to groups such as the BNP and alleged racist and homophobic comments - said it did not condone "unpalatable views".
A spokesman insisted it would not bow to a "political lynch mob".
The row came as emails leaked to the Observer revealed that one of the party's MEPs is concerned about excessive "political correctness" among new recruits.
More top news
The TV quiz star claimed in his autobiography he may have killed a knife-wielding mugger while living rough in Amsterdam in the late 1980s.
Campaigners say scene in which Aidan Turner's character forces himself on a former lover will undermine understanding of consent.
More than 100 cross-party MPs have signed a letter to the US president, stressing their "deep concern" for autistic Lauri Love.