Singer Lily Allen is to join protesters calling for David Cameron to resign as Prime Minister amid public scepticism over his ability to tackle tax avoidance in a demonstration outside Downing Street on Saturday.
The protest comes after Mr Cameron revealed he had benefited from an offshore trust set up by his late father following days of speculation about the Prime Minister's finances.
The hashtag #ResignCameron has been trending in the UK on Twitter throughout Friday and nearly 2,000 people are said to be attending the demonstration, according to a Facebook event.
As well as Lily Allen, comedians Mark Thomas and Josie Long are scheduled to join the protest.
The trade union backed anti-austerity group People's Assembly said they will join the protest, saying the Prime Minister has "lied to the public".
Organisers of the protest, who call themselves "Resign", slammed the Prime Minister as a "hypocrite" and said his position was "untenable".
Mr Cameron has been a prominent campaigner for increased tax transparency and although there is no suggestion the Prime Minister was engaged in any kind of illegal tax evasion, it took five separate statements from aides at Number 10 before he finally admitted that he had owned - and sold - shares in the fund.
Resign has made three demands of the Prime Minister, asking for him to publish his tax returns, rescind an intervention he made to prevent the loosening of how Trust funds are dealt with, and finally, to resign.
They said Mr Cameron's "credibility is now completely shattered on this issue".
Abi Wilkinson, who started the Facebook event, said: "This is an ultimatum for David Cameron. I'm calling for him to sort it out and if he can't, or won't then he needs to resign."
Labour MP John Mann has also demanded the resignation of Mr Cameron, although shadow chancellor John McDonnell said it wasn't "a matter of resignation at the moment".
The calls for Mr Cameron to step down came after he disclosed on Thursday that he had sold his and his wife's shares in Blairmore Holdings - one of the tax haven schemes exposed in the Panama Papers leaks - in 2010 and insisted it was not set up as a tax dodge.
He told ITV News that while his and Samantha's profit from the scheme was "subject to all the UK taxes in the normal ways", it came to just below the threshold at which capital gains tax would have applied. Number 10 said Mr and Mrs Cameron bought their holding in April 1997 for £12,497 and sold it in January 2010 for £31,500.
As well as calls for his resignation, Cameron could face an investigation from the parliamentary standards commissioner, Kathryn Hudson, after Mr Mann said he intends to report the Prime Minister for not declaring his stake in the offshore fund.