This morning it revealed that remedial works to fix the problems will cost at least £20m, but warned it was still assessing the full impact of fixing weld issues.

While Severfield did not reveal where the bridge projects are, HS2 this morning confirmed that nine of bridges were impacted on their scheme.

A spokesperson for HS2 Ltd said: “We have identified a number of welding defects related to steel fabrication work undertaken by one of our suppliers.

“A comprehensive review has been undertaken to determine the extent of the further action required. We are working closely with the company and our supply chain to address the issue.

“This will not impact on the safety or quality of the operational railway which is being designed to the highest standards.”

The extent of Severfield’s problems were exposed for the first time this morning when the firm reported a £6m loss in the first half on sales up 17% at £252m.

In a statement, Alan Dunsmore, chief executive officer, said: “Since the publication of the 2024 results, the group identified some bridge structures which were not in compliance with the client’s weld specification requirements, predominantly relating to twelve bridge projects that are either ongoing or were completed over the past four years.

“The issues all arise out of a particular bridge specification and related sub-optimal choices of welding procedures, exacerbated by limitations in the specified weld testing regime for these projects.”

He said: “A comprehensive review is currently being undertaken by the group, in conjunction with its affected clients, relevant industry authorities and insurers to fully understand the extent of the actions required to resolve the issue, which has not affected the safety of any operational bridges.

“Notwithstanding this, we are continuing our work on ongoing road and rail bridges for a variety of clients, which we are confident will meet the required specification.”

So far Severfield has spent £7.1m on testing and remedial works and expects to incur a further £13.3m cost on eight of the projects.

Severfield added that it still needed to agree solutions on four of the remaining bridge projects where weld testing is ongoing.

As a result, he warned, Severfield was unable to quantify the full extent of its possible exposure based on current information.

“All amounts will be kept under review until our assessment of all affected structures has been concluded.

“The group will be pursuing all potential recoveries from third parties, including insurance, with preliminary indications suggesting a good prospect of insurance recovery, albeit not yet with the level of certainty required for such recovery to be recognised under accounting standards.”

Shares plunged by just over a third in value in early trading.