A subsidiary of British Steel has been sold by the government to the French company Systra in a deal that protects 400 jobs.

The deal is not expected to have any impact on discussions on the rest of British Steel, as exclusive talks continue between the government’s official receiver, the state employee managing the sale, and Oyak, the Turkish military pension fund.

York-based TSP Projects, which designs and builds large rail infrastructure projects, will be folded into Systra. The proceeds of the sale are likely to be allocated to lenders to British Steel, which collapsed into liquidation in May.

Neither the government nor the companies disclosed the sale price but Systra will also take on TSP’s £70m pension liabilities, a hangover from the company’s days as a division of British Rail before privatisation.

Craig Scott, the chief executive of TSP Projects, said the liquidation of British Steel had never threatened his company, which was performing well and counted firms including Network Rail, Siemens and Costain among its clients.

“We would always have found a buyer,” said Scott. He added that he was “pleased to get out from the association with British Steel in administration and to be able to get on with focusing on our business. We’re moving to an owner where we’re part of their core business and it’s a permanent home.”

He said Systra and TSP Projects were growing, meaning that none of the company’s 400 jobs would be lost and more staff could be hired. “We do not have sufficient people to deliver the pipeline we have got coming, so together we need to grow,” he said.

TSP Projects has worked on projects such as the redevelopment of King’s Cross and Reading stations and is also working on infrastructure at Gatwick airport’s station and upgrades to the TransPennine Express rail route.

Most of its employees are based in York but it also has outposts in Birmingham, Manchester, Reading and Bristol.

Systra, an engineering group specialising in transport, is owned by the French state railway companies SNCF and RATP, which runs public transport in Paris, and a consortium of French banks.