Raleys handled 60,000 claims for compensation from ex-miners
Solicitors in South Yorkshire deliberately breached a code of conduct to collect £32m in fees from miners' compensation claims, a tribunal ruled.
Six partners at Raleys in Barnsley took a deliberate and calculated risk to break rules to make "a huge amount".
Partner Ian Firth was suspended for four years, David Barber for two years and Jonathan Markham for six months.
Three junior partners were each fined £10,000. All the solicitors had denied any wrongdoing.
The hearing in London ruled that an agreement made with Zuko Legal, a so-called claims farm, to take on 19,000 claims, some of which were the result of cold-calling practises, was against the professional code of conduct.
The three junior partners fined are Carol Gill, 38, Jim Gladman, 49, and Katherine Richards, 40.
All were named at the tribunal.
Tribunal chairman David Leverton said "every partner knew they were breaching the code by making the agreement".
He said the tribunal took a "serious view" of this and said staff at Raleys made the deal because they realised the practice would "lose their last chance to make a huge amount of money" if they had abided by the code.
The Solicitors' Disciplinary Tribunal was also told the partners compromised their independence and integrity through their close ties with the National Union of Mine Workers (NUM).
The hearing was told the NUM recommended that Yorkshire members seeking compensation for illnesses used Raleys.
A percentage of the workers' payouts then went back to the NUM.
Mr Leverton said the case was a "tragedy for Raleys".
"Years of good service to their community and their clients has been thrown away with their previous reputation," he said.
Gregory Treverton-Jones QC, representing the solicitors, said the lawyers genuinely believed the NUM agreement to be in their clients' best interests, and that they had acted in good faith.
The tribunal heard the firm earned £72m overall for its handling of claims for respiratory disease and vibration white finger.
Mr Treverton-Jones said all the money earned came from legitimate fees, and that the practice was investigated by the Law Society in 2000 for similar issues, but exonerated.
The tribunal ruled Mr Firth, 60, bore a "heavy responsibility" in the case, followed by Mr Barber, 44, and Mr Markham, 46.
Junior partners - Ms Gill, 38, Mr Gladman, 49, and Ms Richards, 40, - played a lesser role.
Mr Treverton-Jones said the ruling was "very hard" for his clients to take, as they acted in good faith and were "committed and able solicitors".
The solicitors were also ordered to pay costs, estimated at more than £800,000, with an interim payment of £300,000 to be paid within 28 days.
Mr Firth must pay 50%, Mr Barber 25% and Mr Markham 15%.
The remaining 10% will be split equally between the three junior partners.