Just a week after Ukip leader Nigel Farage urged the Tories to carry on calling his members rude names because it boosted their support, one MP has duly obliged with the word "Nazi".
In a scorching attack on Ukip, Robert Halfon claimed the party was a good thing because it was "cleansing" the Conservatives of people with abhorrent views.
And he singled out the Ukip Euro MP, Gerard Batten, who has suggested Muslims should sign a charter rejecting violence, saying it was: "literally akin to the Nazis saying Jews should wear a yellow star".
The Tory leadership instantly disowned Halfon's remarks, insisting he was speaking as an individual and was "responsible for his own words", while Farage accused him of engaging in "hysterical slurs".
The outburst has dramatically highlighted both the current Tory panic over Ukip and its confused and contradictory approach to dealing with the threat from Farage and his band of anti-establishment mavericks.
It has also angered party bosses, who fear it will be used by opponents to claim the Tories still have people with such views in their ranks, that they have not all been "cleansed".
And Cameron's Eurosceptic Tory MPs who would like electoral pacts with Ukip will undoubtedly take offence and fear Halfon is pointing the finger at them.
It is notable that it is the popular MP Halfon who delivered the latest assault, because he is the man who urged the Tories to change their name to the Workers Party and adopt a ladder as their logo, as part of a campaign to re-engage with exactly the working class or disengaged voters Ukip can appeal to.
On the one hand there is desperation among the Tory high command to win back supporters who have defected to Ukip, specifically over the linked issues of Europe and immigration, with policies and rhetoric deliberately designed to appeal to them.
On the other, there is a genuine belief that there is a more sinister side to Ukip which is not reflected by the charismatic and engaging Farage but which, they believe, needs exposing.
The two approaches do not fit together and Halfon has chosen to highlight the second in comments that will strike a chord with many politicians who fear Ukip needs to be more closely scrutinised.
The Harlow MP, who is Jewish, told the House Magazine: "To me there are two kinds of UKIP - the Godfrey Bloom guy who's like a cross between Sid James and Bernard Manning, and then there's a much more sinister element, like the MEP who said every Muslim has got to sign a declaration of non-violence, which to me is literally akin to the Nazis saying Jews should wear a yellow star.
"I genuinely find it abhorrent and frightening. I'm amazed that man is still an MEP, how someone could say such a thing and then not apologise for it.
"In many ways Ukip have done us an enormous favour because they're cleansing people from the Tory party that had these kinds of views, which is great because I don't want people who have those kinds of views in my party. So good luck to them, really."
There is no doubt that his remarks accurately reflect a widely-held view of what Ukip is really all about - but which many MPs, particularly Tories, are reluctant to voice in public.