Network Rail has been fined £3m by a court for failings over the Potters Bar train crash, in which seven people died.

The company admitted breaching safety regulations that led to the West Anglia Great Northern train from London to King's Lynn derailing just outside Potters Bar station in Hertfordshire in May 2002.

Passengers Austen Kark, Emma Knights, Jonael Schickler, Alexander Ogunwusi, Chia Hsin Lin and Chia Chin Wu died in the crash. Pedestrian Agnes Quinlivan, 80, was also killed after being hit by debris. A further 70 people were injured.

The track operator admitted it was criminally guilty under the Safety at Work Act for faulty points on the tracks, the responsibility for which it inherited from its predecessor, the privatised company Railtrack.

Jarvis, the engineering company contracted to maintain the track, was also accused over failings in the installation, maintenance and inspection of adjustable stretcher bars which keep some sections of the track at the correct width for train wheels, but the Office of Rail Regulation (ORR) dropped its pursuit of the case after the company went into administration last year.

It had admitted joint liability for the crash after a humiliating apology for trying to blame a saboteur with "informed" engineering knowledge.

Nicholas Hilliard QC, appearing for ORR, said in court that the poor state of a set of points on the track at Potters Bar had made the crash "inevitable".

Following the judgment, Network Rail apologised to victims and said that it had greatly improved safety since the accident.

"Network Rail has today been sentenced for failings that contributed to this accident and we accept the fine as we accept the liabilities inherited from Railtrack," it said. "We say again today that we are truly sorry … We recognise for many that the sorrow remains and we should all pause and reflect as we remember those who lost their lives."

The company said that the £3m fine would be paid from a Treasury fund which builds from savings the company makes from doing work that is cheaper than it budgeted for.

However, the fine is unlikely to satisfy victims' families, who have said others should have been accountable.

Perdita Kark, the daughter of Austen Kark, said: "The fine means we can draw a line underneath this but we won't be satisfied. The whole process shouldn't have taken so long. It's been handled badly and there needs to be a better system for when accidents happen – we shouldn't have to wait nine years."

She added: "Individual directors of Jarvis and Railtrack should have also been fined as individuals to teach companies to take accountability and responsibility. What bothers me ultimately is that the taxpayer is going to foot the bill so I'm paying for the crash which killed my father, which I find insulting. £1m or £5m doesn't really matter."

Network Rail's fine had been expected to run into the millions after the company received a £3.5m fine for failings in the Hatfield rail crash in 2000, which killed four and injured 102. The company also inherited responsibility for that crash from Railtrack. Balfour Beatty, which was responsible for maintaining the broken section of track that caused it, was originally fined £10m, which was reduced to £7.5m.

Network Rail, which owns the UK's tracks and stations, sought mitigation in view of Jarvis's role in the crash. It is government-backed and received a £3.7bn annual government grant last year. Some victims' families are angry that the fine will therefore be largely funded by the taxpayer.

Louise Christian, a solicitor who represented victims' families during the inquest into the deaths last July, has called the proceedings a "charade".

"They deliver no accountability," she said. "The only person paying the fine is the taxpayer ... It could be a substantial fine but you need to ask what the point is."