Spain’s Transport Minister Óscar Puente has resigned – six days after the high-speed train collision in which at least 69 people were killed and dozens injured.

He announced his decision in Congress, where he was giving evidence on the circumstances of last Wednesday’s crash near the town of Urda, south of the capital Madrid.

“A transport minister in a country like Spain cannot remain in office after two accidents of this seriousness in less than a year,” he said, also referring to a deadly crash in January in Andalusia, southern Spain

The latest tragedy in Urda happened when a state-operated Renfe high-speed train smashed into the back of another stationary train operated by the Iryo company.

Puente announced his decision at the end of a congressional session on Tuesday evening in which he had outlined new rail safety measures and been grilled by the opposition.

He said he had taken the decision to resign immediately after the 28 October disaster, but had not made it public.

Puente had been under mounting pressure in the wake of the disaster as opposition parties and some allies of the government called on him to step down.

His resignation comes as a blow to the Socialist-led government ahead of a general election set for 29 November.

During his lengthy hearing before lawmakers, Puente said: “I wish to inform you that I am not only stepping down from my position as minister of transport, but that I am also withdrawing my name from the lists for the early legislative elections.”

Leaked audio recordings published in Spanish media soon after the crash revealed conversations between train drivers and a control centre just minutes before the disaster.

The three recordings of conversations between Madrid’s control centre and two train drivers appear to show that one high-speed train was given clearance to move even though another train had stopped on the track, about 25km (15 miles) ahead.

Prime Minister Pedro Sánchez has said that authorities will “get to the bottom of every last detail of this tragedy”.

Last week’s crash was one of the worst rail disasters in Europe’s modern history, and Spain’s worst crash since 2013. The country observed three days of mourning after the tragedy.

The moving train, run by state-owned operator Renfe, had 397 passengers on board. The stationary train was run by private operator Iryo, and carrying 147 passengers.

A reported issue with the automatic signalling system – a computer failure – had forced all trains to halt on the affected stretch.

But later the Renfe train was ordered to proceed in “error”, according to Puente.

The audio recordings were published by several Spanish news outlets including El Pais and RTVE.

In one, a control centre operator is speaking to the driver of the Renfe train, which was having some technical difficulties.

After some exchanges, the control operator tells the driver: “Continue your journey and then proceed under [Lateral Signalling Block], at normal speed with normal operation.”

The driver replies: “At normal speed?” To which the controller answers: “Yes.”

The Lateral Signalling Block is a back-up or alternative train system used when the automatic signalling or data transmission system fails.

The driver of the stationary Iryo train says in another audio recording that communication with the train-control system has been lost, and it is not moving.

The train “is stationary in front of the entry signal at Urda”, the driver tells the control centre operator. After a series of exchanges, the driver is then told to “resume the journey” normally.

The Iryo driver then contacts the control centre again, according to a later recording, saying they cannot start the train. “The train won’t allow me to control the [security] system. That’s why I am still stopped in front of the entry signal,” they say.

The latter recording suggests that the controller had been notified that the Iryo train remained stationary as the Renfe train approached.

Iryo said its carriages were “struck from behind” by the other train.

Puente said last week that the decision to instruct the trains to move again, without any speed restrictions, was “inexplicable”.