Nina Jensen, who heads the green pressure group WWF in Norway, sent out her Twitter attack on Thursday as Norway's governing parties debated their political programme with the minority Christian Democrat and Liberal parties.
"Do not let yourselves be sweet-talked by Siv Jensen," she tweeted to Christian Democrat Leader Knut Arilde Hareide. "SPU [the government pension fund] must be pulled out of coal companies now. "
.@KAHareide @Trinesg: Ikke lar dere sweetalke av Siv Jensen. SPU må trekkes ut av rene kullselskaper nå, resten kan utredes videre.
— Nina Jensen (@Nina_Jensen) February 27, 2014
"It's not me who is the best at sweet-talking in the Jensen family :-)," her sister quickly tweeted back.
Hareide then neatly sidestepped the spat by pointing out that, as he was on paternity leave, he was not involved in the negotiations anyway.
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"I can promise that it's only these two ladies I'm sweet-talking at the moment," he tweeted, attaching a picture of his wife and new daughter and signing off as "pappa-leave Knut".