Chinese steel being imported into the UK could be putting lives and buildings at risk, as well as jobs.

Additives in some Chinese steel used to reinforce concrete can affect the metal’s strength when it is welded and now UK industry is highlighting the dangers posed by it.

Chinese steel makers sometimes add boron to their products to get a tax rebate as it was classed as an alloy.

When the steel joined by arc welding, boron can make welds more likely to crack, weakening structures.

The risk comes from current regulations not requiring steel-makers to specify how much boron has been added if the steel is used for reinforced bar – or rebar – which is added to concrete to strengthen it.

This means that construction companies could unwittingly use steel which could pose a risk because it is being welded using techniques that could weaken it.

The danger is growing as imports of steel from China rise. In 2013, just 2pc of rebar was imported from China, while today 39pc of 308,000 tonnes required by UK construction comes from the country.

Now UK Steel, industry trade body the British Association of Reinforcement and steel unions have warned of the dangers that imported steel could pose.

Roy Rickhuss, general secretary of steelworkers’ union Community, said: “I am very concerned that UK construction workers’ safety is being put at risk by imports. There needs to be clarity throughout the supply chain about the levels of added alloys.

“Given that there are tens of thousands of tonnes of Chinese imports at UK ports or in the supply chain, clarity is desperately needed to avoid unnecessary risks.”

Gareth Stace, director of UK Steel, said: “The danger is from the regulations because people may not know what the steel they are using contains. If they do they can use different types of welding to compensate.

“We are currently asking the British Standards Institute (BSI) to make a simple amendment to regulations, which would ensure that consumers of rebar know what they are buying.”

Construction companies are now being urged to only use steel whose provenance can be traced, under the Charter for Sustainable British Steel campaign.

According to UK Steel, Britain produces about 12m tonnes of steel a year, but Chinese mills have an annual overcapacity of 250m tonnes and dumping the surplus abroad.

The news comes just weeks after Tata said it would cut up to 720 jobs at its steel works in Rotherham, South Yorkshire, because it could not compete with cheap imports from China.

Karl Koehler, chief executive of the company’s European operations, said “cripplingly” high energy costs in Britain and the strong pound meant Tata could not compete on price in the face of cheap imports from China.