With echoes of the movement that toppled Icelandic Prime Minister Sigmundur David Gunnlaugsson, UK PM David Cameron must make tax avoidance impossible under British law or resign from office, activists are demanding.

The hashtag #resigncameron is trending at the top on Twitter at this moment, hours after Cameron admitted to having held shares in his late-father’s offshore investment fund, Blairmore Holdings, which avoided paying tax in the UK.

Cameron made this admission on Thursday night in an interview with ITV. He claims to have sold them for about £30,000 (US$42,000) before taking office in 2010.

A protest outside 10 Downing Street is scheduled for Saturday, along with a spate of smaller regional demonstrations across UK.