Spain's worst train disaster in decades, which killed 79 people last year, was caused by excessive speed and the driver's failure to brake in time, according to a report by the country's Public Works Ministry.

The train derailed and smashed into a wall on the outskirts of the northern city of Santiago de Compostela on July 24 last year, after approaching a curve at more than twice the speed allowed on that stretch of track.

The ministry's report, published on its website, will be taken into account by the regional court in Galicia which is leading the investigation.

The train's driver, Francisco Garzon, has been charged with 79 counts of homicide, while 11 former high-ranking officials from state railway company Adif have also been charged in connection with the case, for potentially failing to adequately ensure passengers' safety.

"The accident was caused by the train's excessive speed (...) and because the driving personnel did not respect the rules," the final report by a train accident investigation commission, which is part of the ministry, said.