Utility firm Transco has been fined £15m - a UK record - after being convicted on a charge arising from an explosion which killed four people.
The wreckage of the Findlays' home in Larkhall
Andrew and Janette Findlay and their children Stacey, 13, and Daryl, 11, died in the explosion in Larkhall, South Lanarkshire, in December 1999.
Transco was found guilty after a six-month trial in Edinburgh of breaching health and safety laws.
The blast, caused by a leaking gas main, destroyed the Findlays' home.
The £15m fine will not go to the family but directly into the public purse, BBC Scotland Home Affairs correspondent Reevel Alderson said.
The judge, Lord Carloway, said that Transco had not shown any remorse for the tragedy.
In a statement after the verdict, Transco said it was disappointed with the outcome.
The firm said: "What happened at Larkhall in December 1999 was a terrible tragedy and our thoughts remain to this day with the families and community who were so affected by it.
"The company is disappointed with the verdict and will now consider the judgment in detail prior to deciding whether or not to take any further action."
The previous largest fine in the UK under a health and safety prosecution was £2m, imposed on Thames Trains after the Ladbroke Grove accident in which 31 people died.
The court heard that in March 2005 Transco had a £390m operating profit on a turnover of £2.2bn.
Four members of the Findlay family died when their house in Carlisle Road, Larkhall, was totally destroyed in the early morning blast.
A statement on behalf of the families of the victims said: "We are pleased with today's verdict which means Drew, Janette, Stacey and Daryl can now rest in peace. They remain forever loved and forever missed.
"The verdict does not change the fact that our two families will never be the same.
"However, we take some small comfort from the hope this verdict brings that no other family should ever suffer as we have.
"We only ever wanted truth and justice."
The jury began deliberating on Monday after hearing 26 weeks of evidence and a week of legal submissions.
On Thursday, it returned a verdict finding Transco guilty under health and safety legislation.
Transco was convicted of failing to maintain the iron gas main which ran through the Findlays' garden when it was extensively corroded and leaking.
Janette and Drew Findlay died when their home blew up
The case centred on maintenance, repair and record keeping procedures.
The indictment alleged Transco failed to keep accurate records of its pipelines, including the iron main which the company believed was made from polyethylene.
The firm was also found guilty of failing to ensure that members of the public were not exposed to risks to their health and safety.
Health and Safety Executive spokesman John Sumner paid tribute to the investigators involved and offered condolences to the relatives of those who died.
Mr Sumner added: "The conviction sends a message not just to Transco but to all operators of hazardous plant of the need to keep accurate records, operate effective management systems and properly maintain pipelines and equipment."
Strathclyde Police Detective Chief Superintendent Ruaraidh Nicolson said the inquiry had been a unique and tragic investigation for the force.
He said: "We hope today's judgement will bring some comfort to everyone effected by the catastrophic events of 22 December, 1999, and allow them to look to the future. Our thoughts are with the family today."
Their children Daryl and Stacey were killed in the blast as well
The Crown Office also recognised the commitment and professionalism of the investigating team.
A spokesman said: "Everyone working on this case was aware that at its heart were families who had been devastated by the events of 22 December 1999. Our thoughts remain with these families."
Transco is no longer responsible for Scotland's gas supply network. The firm sold it earlier this year and it is now owned by Scotia Gas Networks, which is part of Scottish and Southern Energy.
Local MSP Karen Gillon has renewed her call for senior managers to face charges in cases of corporate negligence.
A fridge was blown onto the roof of another house in the explosion. One witness described the scene as like a "war zone".