Downing Street has refused to say if David Cameron's family still has money in an offshore fund after his father was named in the 'Panama papers'.

Ian Cameron was described as instrumental in the setting up of Panamanian firm Blairmore Holdings, named after the family home in Aberdeenshire.

The company, which reports suggest paid no tax for decades, helped build up a significant legacy some of which the Prime Minister inherited.

Reports suggest that peers, former MPs and dozens of party donors are still to be named following the release of more than 11 million documents, thought to be the biggest data leak in history.

The papers relate to investments set up by a law firm in Panama, Mossack Fonseca.

Within hours of the news breaking UK tax officials asked for access to the documents to investigate allegations of money laundering and tax avoidance.

A number of world leaders also came under fire, including the Prime Minister of Iceland, who faced calls to resign over claims of an undeclared interest in his country's bailed-out banks.

No 10 refused to say whether or not the Cameron family still had funds in offshore investments, saying that the issue was a "private matter".

Downing Street also said that similar reports about Ian Cameron first emerged four years ago.

But the focus on the Prime Minister's father led to accusations that Mr Cameron has failed to deliver his pledge to open up UK crown dependencies and overseas territories which act as tax havens and calls for "real action".

No 10 insisted that the Prime Minister was leading efforts to make international tax arrangements more transparent.

Asked if he was prepared to force action through legislation, his official spokeswoman said: "He rules nothing out".

The Foreign Secretary Philip Hammond, who recently met the Panamanian vice president, also said that "significant progress" had been made.

He welcomed the leak, saying that it would remind those who were "up to no good how fragile and how vulnerable they make themselves by indulging in this kind of activity".

But Labour leader Jeremy Corbyn said it was "time to get tough on tax havens".

"Britain has a huge responsibility, " he said. "Many of those tax havens are British overseas territories or Crown Dependencies.

"As the leaked documents show, tax havens have become honey pots of international corruption, tax avoidance and evasion.

"The Government needs to stop pussyfooting around on tax dodging."

He also called for extra resources for Her Majesty's Revenue & Customs (HMRC) to help the tax authorities mount a crackdown.

The SNP's deputy leader Stewart Hosier said that the ownership of many companies registered in British Overseas Territories was "shrouded in secrecy... making it impossible for tax authorities to find out who really owns and benefits from the company.

"This has to stop and the Tories are running out of excuses."

The Liberal Democrat leader Tim Farron called for an independent investigation saying that the UK Government had "failed to act".

The files reportedly include a suspected £1.4 bn money laundering ring run by a Russian bank said to involve close associates of President Vladimir Putin.

The Kremlin denied the president was connected to any wrongdoing and claimed he was the victim of "Putinophobia".

There were also claims that money from the Brink's Mat robbery was laundered using a company set up by Mossack Fonseca.

In China, relatives of at least eight current and former members of the politburo are alleged to have hidden wealth offshore.

Mossack Fonseca said it had operated "beyond reproach" for 40 years and had never been charged with criminal wrongdoing.

Mr Mates is said to have been linked with offshore companies used for real estate development in the Bahamas.

He said the company "never had any real value".