The man in charge of overseeing the UK Government's inquiry into the Panama Papers was a partner at a law firm that acted for the offshore fund set up by David Cameron's stockbroker father, it emerged this morning.

Edward Troup, executive chairman of HMRC, was a partner at Simmons & Simmons, which represented Ian Cameron's Blairmore Holdings and other offshore firms named in the leak.

HMRC has been given a lead role in the £10million taskforce launched to investigate allegations of wrongdoing highlighted in the 11.5million documents leaked from Panamanian law firm Mossack Fonseca.

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HMRC chief Edward Troup, left, is a former partner at Simmons & Simmons, which reportedly represented Ian Cameron's (right) Blairmore Holdings and other offshore companies named in the Panama Papers leak

The files - leaked last week - have revealed how wealthy businessmen and political elites from across the world managed to hide their money in tax havens.

Mr Cameron became embroiled in the row after it emerged Blairmore Holdings - the offshore fund that was run by his late father - was among the firms registered as Mossack Fonseca's clients.

After days of silence the Prime Minister was forced to admit on Thursday that he held a £30,000 stake in the Blairmore until he sold it before entering Downing Street in 2010.

There is no suggestion of wrongdoing by Simmons & Simmons or any of its clients.

His handling of the revelations caused the most damaging week of his premiership and yesterday he took the unprecedented step of publishing details of his tax affairs in a bid to clear his name.

HMRC will be working alongside the National Crime Agency as part of the inquiry into claims of tax dodging and money laundering that were brought to light in the Panama Papers leak.

But Shadow Chancellor John McDonnell has demanded a full, independent inquiry, saying it must have the 'full confidence of the British people'.

Simmons & Simmons' name appears on dozens of emails and documents in connection with a number of companies registered with Mossack Fonseca, according to the Guardian.

Some date back to 2003, when Mr Troup was still a partner. The first leaked correspondence regarding Blairmore Holdings date from 2005, a year after Mr Troup left to join the Treasury. He joined HMRC in 2013 and was named chief executive in April.

HOW THE LEADERS COMPARE: DETAILS REVEALED AFTER CAMERON, CORBYN, BORIS, OSBORNE AND STURGEON PUBLISH THEIR TAX RETURNS Salary Additional income Tax paid David Cameron £œ140,522 £œ49,951 £œ75,898 Jeremy Corbyn £œ67,060 £œ1,850 £œ18,912 Boris Johnson £œ127,505 £œ491,978 £276,505 George Osborne £120,526 œ£78,209 £œ72,210 Nicola Sturgeon £œ104,817 œ£0 £32,517

Simmons & Simmons' name appears on dozens of emails and documents in connection with a number of companies registered with Mossack Fonseca, whose Panamanian headquarters is pictured above

The Panama Papers appear to show Simmons & Simmons' offices in London and Hong Kong were registered as clients or intermediaries with Mossack Fonseca.

It was also reported that In 2008, when Blairmore was considering a change of jurisdiction, Simmons & Simmons asked Mossack Fonseca for advice on the benefits of other tax havens.

HMRC said Mr Troup had never had dealings with Mossack Fonseca and none of the individuals or organisations named so far in relation to the Panama Papers were clients he had advised.

Shadow chancellor John McDonnell, pictured, has called for an independent inquiry into the leak

But Labour has stepped up demands for an independent inquiry into the leak in the wake of the latest revelations.

Shadow chancellor John McDonnell said: 'This further highlights why, for any inquiry to have the full confidence of the British people, it must be truly independent in structure and process.

'It certainly should not be reporting to politicians whose party has been highly implicated in this scandal, with large donors directly involved in this matter.

'But most of all it needs to be above question and beyond rebuke.

'And with new allegations calling the Government's approach into question the only obvious answer is a truly independent public inquiry as Labour is demanding.'

A HMRC spokesman said: 'Before joining the Civil Service in 2004, Edward Troup had a successful career in the private sector, during the course of which he dealt with many companies.

'He can confirm that he never had any dealings with Mossack Fonseca, was unaware of the company until recently, and that none of the individuals or organisations named so far were clients that he advised.

'Edward Troup's role in HMRC has never involved responsibility for operational activities or direct dealings with companies on their tax affairs.

'In any event, the governance in place at HMRC means that any commissioners who have a potential conflict of interest would exclude themselves from any investigation or settlement involving a taxpayer with which they had had dealings in their previous careers.'

It comes after Eurosceptic Tories rallied to David Cameron’s support last night in the row over his tax affairs.

They accused Labour politicians of acting like 'hyenas' for tearing into the Prime Minister over his tax arrangements, which have not revealed any wrongdoing or illegality.

Michael Gove, Tory justice secretary and Brexit campaigner, said it was ‘crystal clear Mr Cameron had acted with integrity and probity throughout’.

Mr Cameron became the first Prime Minister to publish details of his tax returns dating back to 2009 in a bid to ease criticism of his mother and late father.

Labour leader Jeremy Corbyn said the disclosure did not go far enough, and demanded more details on whether Mr Cameron had profited from his father’s Panama-registered Blairmore fund.

He also faced criticism over a £200,000 gift made to him by his mother Mary, despite experts saying the move was a normal part of inheritance tax planning of the type used by thousands of middle-class families.

The Prime Minister, who admitted at the weekend he should have been quicker to reveal his finances, will hit back today in the Commons with a passionate defence of his parents and their actions.

Simmons & Simmons did not respond to the Guardian's request for comment. MailOnline has contacted the law firm for comment.

HOW CAMERON'S FAMILY CARVED UP THE INHERITANCE CASH FOUR YEARS BEFORE HIS FATHER DIED (From left) The Prime Minister's siblings Alexander Cameron QC and Tania Cameron Four years before Ian Cameron died, his Oxfordshire family home was transferred to his eldest son Alexander, a wealthy QC. As part of the deal, Mr and Mrs Cameron senior moved into Alexander's smaller home next door. Because it was handed over more than three years before Ian died, the full 40 per cent inheritance tax on the £2.5 million home would not be payable: the rate 'tapers' down to nothing if the deceased survives for more than seven years. At the time, only the first £325,000 of an estate was free of inheritance tax, so if the house's value was taken in isolation from the rest of the estate, Alexander would have paid 24 per cent on the £2.1 million of the house which was taxable. Separately, David Cameron's two sisters, Tania and Clare, were jointly left in the will a £1 million London house. The two women, who shared the house equally, had already been gifted a stake of unknown value in the property in advance of Ian Cameron's death. Advertisement

Now heat is on Chancellor to reveal tax dealings as senior Tory says it's 'inevitable' that all MPs will publish their returns

Tory MP Jacob Rees-Mogg has pledged to release his tax return information

George Osborne is under mounting pressure to reveal details of his income and tax dealings amid claims it is now 'inevitable' all MPs will have to publish their returns.

Sources close to the Chancellor made clear he is considering whether to follow David Cameron's example by releasing information about his finances.

Downing Street disclosed a summary of the Prime Minister's tax returns covering the past six years in a bid to restore trust after a disastrous week of revelations about links to his father's offshore investment fund.

They showed that Mr Cameron had an income of around £1.1 million over the period and paid some £400,000 in tax. Renting out his London home while he lives in a grace-and-favour apartment has been bringing in more than £90,000 a year.

Labour has lashed out at the revelation that Mr Cameron received gifts totalling £200,000 from his mother Mary after the death of her husband Ian in 2010.

If he had received the money as an inheritance it could have attracted duties of up to £80,000.

Shadow chancellor John McDonnell has already published a copy of his tax return, and Labour leader Jeremy Corbyn has promised to do so soon.

A Treasury source said 'no decision has been taken' on whether to release Mr Osborne's information. He is said to be 'happy to consider ways to offer more transparency'.

But the source insisted his income came from his salary, rental from letting out a home while he lives in Downing Street, and a shareholding in his father's wallpaper business Osborne & Little.

They also stressed that there was no suggestion the Chancellor had money offshore.

Tory backbencher Jacob Rees-Mogg upped the pressure by saying he believed it was 'inevitable' that all MPs will now have to publish their tax returns.

'I think I am going to have to,' he told BBC Radio 4's Today programme. 'I am not going to be the one hold-out about that.'

Mr Cameron, who admitted at the weekend he should have been quicker to reveal his finances, will attempt to regain the initiative in a Commons statement where he is expected to make a passionate defence of his parents and their actions.

He will also confirm that the government is launching a crackdown on companies that facilitate tax evasion.

A new law being brought forward this year will make it a criminal offence for companies to fail to stop staff aiding tax evasion.

The move was first announced in the March 2015 Budget, when Mr Osborne said the Government would introduce the measure in this Parliament.

Speaking ahead of his statement, Mr Cameron said: "This Government has done more than any other to take action against corruption in all its forms but we will go further.

"That is why we will legislate this year to hold companies who fail to stop their employees facilitating tax evasion criminally liable."

Eurosceptics have put aside their differences with the Tory leadership to condemn Labour attacks over Mr Cameron's finances.