James Beresford (58) and Douglas Smith (51), from Doncaster firm Beresfords, deny 11 allegations in relation to how they handled claims by thousands of ex-miners for industrial diseases.

And the tribunal will also look into alleged improper deals made by the two partners with officers from the Mansfield-based Union of Democratic Mineworkers (UDM) and its claims handling firm Venside.

The hearing, before the Solicitors' Disciplinary Tribunal, is set to last until next week and if the pair are found guilty of misconduct they could be struck off, suspended, fined up to £5,000 per allegation or reprimanded.

The tribunal is being held after an investigation into how law firms wrongly took money from miners' compensation payouts, when they were already receiving payment from the Government for handling the cases.

Mr Beresford has been dubbed 'Britain's richest solicitor' by a national newspaper, which says he made £17m in one year from handling miners' claims.

Among the allegations labelled against the pair by the Solicitors' Regulation Authority are that they acted where there was a conflict of interest, failed to act in the best interest of clients and did not give enough information to clients about the funding of claims.

And it is also alleged the two partners at Beresford shared their professional fees with a non-solicitor — Walker & Co — which was run by Clare Walker, who worked as the UDM's claims manager.

A spokesman for the Solicitors' Regulation Authority told Chad: "This is an exceptionally complex case. Tribunal cases don't normally last this long — we anticipate it will end some time next week."

In 2006, UDM general manager Mick Stevens and Clare Walker temporarily stood down from their positions at the union after the Serious Fraud Office launched an investigation into the UDM's handling of miners' compensation claims