David Cameron's personal approval ratings have plummeted after it emerged his father, Ian, was a client of Mossack Fonseca, the Panamanian law at the centre of a major tax avoidance scandal. The crisis has hit the prime minister in the opinion polls, with just weeks to go before the local and assembly elections across the UK on 5 May.

A survey from YouGov, of more than 1,600 people between 6 and 7 April, showed that Cameron's net approval rating had dropped from -14 in February to -24 – the lowest level since July 2013. But Labour leader Jeremy Corbyn has seen his popularity surge from -34 in February to -22 in April.

The research also revealed that Cameron (23%) and Chancellor George Osborne (17%) were significantly less trusted to deal with the issue of tax avoidance and tax havens than Corbyn (39%).

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The poll was conducted before Cameron eventually admitted he sold £31,500 worth of shares in Blairmore Holdings, which was set-up by his father in Panama and operated out of the Bahamas, before Cameron was elected in 2010.

"I paid income tax on the dividends, but there was a profit on it but it was less than the capital gains tax allowance, so I didn't pay capital gains tax, but it was subject to all the UK taxes in all the normal ways," the prime minister told ITV News.

"So I want to be as clear as I can about the past, about the present, about the future, because frankly, I don't have anything to hide."

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Cameron has promised to publish his personal tax return "as soon as possible", while Labour MP John Mann has called on the prime minister to resign. Meanwhile, HM Revenue and Customs (HMRC) has launched an investigation into the so-called Panama Papers.

"It is now incumbent on the prime minister to reassure UK taxpayers by listing all the investments he held since becoming Tory leader," said Labour deputy leader Tom Watson.

"Only by stepping out of the shadows and into the sunlight will David Cameron be able to disinfect his sullied reputation. Those Panama Papers confirmed this week that when it comes to avoiding tax, half the Tory establishment are experts at it."