The rail minister Peter Hendy has apologised for emails in which he threatened to withhold contracts from a supplier whose engineer had publicly raised safety concerns about overcrowding at Euston station.

Lord Hendy told an industry conference in London that the tone of his messages sent in his previous role as chair of Network Rail “fell well short of what should be expected, and for that I apologise”.

Hendy sent the emails to the consultancy Systra and to officials internally after Gareth Dennis, a railway engineer and writer, made comments in a newspaper interview about the safety of the notoriously overcrowded London rail hub.

Hendy wrote to Systra’s chief executive, Nick Salt, in May asking “what action are you taking?” over Dennis, who had said Euston was sometimes “unsafe” because of the number of passengers waiting for trains.

The letter warned: “Finding a potential supplier criticising a possible client reflects adversely on your likelihood of doing business with us or our supply chain.”

He also told Network Rail officials to “deal with” the engineer, and said the Systra CEO should be sent a “stop and desist” letter with a request for disciplinary action against Dennis.

Asked about the emails on Wednesday at the Railway Industry Association conference in London, Hendy said safety was “an absolute priority for Network Rail” and it had acted quickly on concerns raised by the regulator, which were “closed down before the end of that year, months before the article”.

But, he added: “There was a sentence at the end [of the letter] where the tone of it fell well short of what should be expected, and for that I apologise.

“And what I would say is that no contractor has or will be penalised for employees raising concerns about safety.” He added: “The employment decisions about the person concerned are a matter for his employer.”

Dennis, an award-winning rail professional, was suspended and subsequently sacked by Systra after Hendy’s intervention.

Responding to the comments on Wednesday, Dennis, who is still jobless, said: “Hendy is only apologising for the tone of his letter – nothing on his subsequent threats by email – to calm the anger of a supply chain he was seemingly willing to threaten and cajole. He is not apologising for the harm he has caused me or the damage he has caused to the rail industry’s public reputation.

“For the rail industry to be confident that its safety culture doesn’t take second place to reputational culture, he needs to make an unequivocal apology for his letter and for having me removed from my job.”

Last month, Network Rail announced immediate plans to tackle overcrowding problems at Euston station and improve the passenger experience after criticism from ministers, watchdogs and the regulator.

Hendy also promised to provide greater certainty for the industry, as he said it needed to rebuild “confidence and trust” after sudden recent changes by the last government, including the “peremptory decision of the last government to abandon HS2 phase 2”.

“I can probably tell you more than most of you know about how quickly that was taken – and how few people knew what the decision-making process was,” he said. “There were, frankly, far more projects left by the previous government than the funding available.”

Hendy said that the spending review would allow the Treasury “to ensure that our rail projects align with financial realities, and, importantly, a 10-year infrastructure strategy.”

Sir John Armitt, chair of the National Infrastructure Commission, said a decade was the minimum needed to ensure building of major projects.

He told the conference that the government’s announcement it would fund the completion of HS2 tunnels to central London was welcome, but added: “That’s the relatively straightforward bit. The real challenge is Euston station, which will take longer to do than it will to drive the tunnels. So what’s really needed is to find a solution to dealing with Euston.”

Armitt said he was awaiting details of a rail strategy for the north, saying: “The fundamental question, of course, is, where’s the money?”

But, he added: “In terms of HS2, we’ve got to tell the country, this is important – and get on and deliver it.”