Large protest on Downing street calling David Cameron to resign over Panama Papers news

David Cameron has said he must take the blame for the way Downing Street handled revelations about his interest in his late father’s offshore investment fund, and suggested he will imminently publish details of his personal tax affairs.

Addressing the Conservative party spring forum, the prime minister admitted it had “not been a great week”, to laughter from the gathered supporters.

Cameron said he would publish details of his tax return “later on” as he attempted to assuage calls for further transparency about his financial dealings.

“I know I should have handled this better,” he said. “I could have handled this better. I know there are lessons to learn and I will learn them. And don’t blame No 10 Downing Street, or nameless advisers, blame me. And I will learn the lessons.”

As Cameron addressed his party’s supporters, thousands of protesters gathered outside the gates of Downing Street calling for him to resign.

The crowd then marched to the forum at the Grand Connaught Rooms, in Covent Garden, wielding placards and chanting for him to step down.

Cameron told the forum he was “very angry about what people were saying about my dad”.

“I love my dad. I miss him every day,” he said. “He was a wonderful father and I’m very proud of everything he did.

“But I mustn’t let that cloud the picture. And the facts are these. The facts are I bought shares in a unit trust, shares that are like any other sorts of shares, and paid tax on them in exactly the same way. I sold those shares, in fact I sold all the shares that I owned on becoming prime minister.

“And later on I’ll be publishing the information that goes into my tax return, not just for this year but for years gone past because I want to be completely transparent and open about these things. I’ll be the first prime minister, the first leader of a major political party, to do that, but I think it’s the right thing to do.”

After a torrid week, which ended with calls from MPs for his resignation, Cameron aimed to move the focus to his party’s record as he launched the Conservative campaign for next month’s local elections.

In his speech at the forum, Cameron said: “One year into our second term and no one can deny: we are doing big things.”

The prime minister was accused of misleading the public after he issued several statements before finally admitting he had benefited from his late father’s offshore investment fund Blairmore. The details of the fund were contained in documents leaked from the Panamanian law firm Mossack Fonseca. 

The revelation came amid infighting over the forthcoming EU referendum and just weeks after the work and pensions secretary, Iain Duncan Smith, resigned over proposed welfare cuts. The government is also facing the potential collapse of the British steel industry after Tata Steel announced it planned to pull out of all its UK operations, putting 15,000 jobs at risk.

YouGov research released on Friday revealed Cameron’s approval rating was at its lowest level since July 2013 and was below that of Jeremy Corbyn for the first time. Of those surveyed, 34% said Cameron was doing well as prime minister, while 58% said he was doing badly, giving him an overall rating of -24. By comparison, the Labour leader’s rating was -22, after 30% said he was doing well and 52% that he was doing badly. 

Corbyn said on Saturday he would publish his own tax return “very, very soon” and insisted there were “no surprises there” as he demanded action to crack down on tax havens.

The Labour leader said Cameron had painted a confusing picture over his tax affairs and suggested the prime minister should reveal details about the Blairmore Holdings trust as well as his own finances.

“He has made a series of statements over the week which are somewhat confusing,” Corbyn told Sky News. “We have finally reached a position where he is going to publish his tax return, apparently, and also tell us how much money was made from this offshore trust, what tax he paid and what tax was paid by the trust.”

Corbyn has called on Cameron to address MPs on his private financial dealings when they return to parliament next week.

“It is now clear that the prime minister has misled the public about his personal involvement in offshore tax avoidance schemes,” he said on Friday. “It took five weasel-worded statements in five days for the prime minister to admit that he has personally profited from an undeclared Caribbean tax haven investment deal.

“After years of calling for tax transparency and attacking complex offshore tax arrangements as ‘morally wrong’, the prime minister has been shown to have personally benefited from exactly such a secretive offshore investment.”

On the campaign trail in Edinburgh, ahead of the Scottish elections, Corbyn reportedly made further remarks about Cameron’s finances.

“I think we also need to look at parliamentary rules on this so it’s absolutely clear there has to be a declaration of income from overseas sources as well. At the moment, it is slightly blurred,” reported Buzzfeed.

He called on all politicians to publish their tax returns, saying: “You should put into the public domain what your levels of income are, where it’s come from and the tax that’s paid on them. That’s the correct way of doing it.”

As part of attempts to reconcile the Conservative party, Chris Grayling, the leader of the House of Commons, who wants Britain to leave the EU, spoke out in support of the prime minister, who is leading the campaign for Britain to remain.

“When it’s a matter that relates to your late father, first of all you don’t know all the information yourself about what your father’s affairs were and secondly you’re very protective of your father,” Grayling told BBC Radio 4’s Today programme.

“When the story that’s coming out of Panama is all about how some pretty unpleasant international dictators are hiding money in Panama, then it’s a very difficult question for a family when frankly nobody’s done anything wrong.”

Downing Street’s series of statements denying that the prime minister, his wife or children held any shares or would benefit in the future from offshore funds or trusts were capped off when Cameron made a fifth statement – in an interview with ITV News – in which he admitted he had sold his shares in 2010 for £31,000, making a profit of £19,000.

It remains unclear whether Cameron’s direct relatives, including his mother, Mary, held money in offshore trusts, and whether his £300,000 inheritance included money accrued from tax haven investments.

There has been no further clarification from No 10 about what investments the prime minister and his family may have held in Jersey, following further reports.

Meanwhile, the governments of two tax havens have repeatedly ignored British ministers’ requests to discuss cracking down on tax avoidance of the kind detailed in the Panama Papers, according to the Independent.

Official letters obtained under freedom of information laws show ministers were “disappointed” at being stood up after numerous attempts to meet the leaders of the British Virgin Islands and Cayman Islands.