Tata Steel underscored a troubled year for India’s largest private steelmaker, punctuated by huge write-offs and the looming threat of industrial action in the UK, as it unveiled fourth-quarter results in Mumbai on Wednesday evening.

Weak demand, sharp increases in steel imports and higher costs in India, along with slumping steel prices internationally due to a Chinese supply glut, led the steelmaker to report a below expectations $615m net loss for the full year and a $890m loss in the fourth quarter.

In what JPMorgan analysts described as another “kitchen-sinked quarter” for India metals, Tata Steel joined Vedanta Resources, which recently took a $3.1bn charge, in writing off huge value from its business.

Tata last week wrote off about $785m, largely from its European business, bringing its total provision for the full year to near $1bn. It was the second writedown in two years for Tata’s European steel assets, after a $1.6bn charge in 2013.

Since acquiring Anglo-Dutch steelmaker Corus in 2007 for $13.1bn, Tata’s European business has been forced to slash costs and cut jobs as it struggled amid dramatically falling demand.

The recent writedown was concentrated in the UK section of its European long products division, which has now been written down to zero, according to the company.

Speculation that Tata could soon sell the European long products division, which makes steel for building and to make rails for train lines, has been rife since the company entered into talks with Geneva-based industrial group Klesch in 2014.

However, Karl Koehler, chief executive of Tata Steel Europe, said that “the triggers for a sale are different” and the writedown “does not really impact negotiations”.

Any buyer would have to deal with threat of industrial action at Tata Steel UK after the company announced plans to close the British Steel final-salary pension scheme in March. Tata had estimated that the closure of the scheme would result in savings of £1bn.

Without clarity around the strike, “even the Klesch group may not be able to complete its purchase of EU long products business,” said Credit Suisse’s India equity team earlier in the month. Tata told reporters it expected talks to conclude in a “couple of months”.

On Wednesday, UK-based Unite became the latest union to announce plans to ballot its 6,000 members for strike action over the pension closure. Steel unions Community, GMB and Ucatt have already begun balloting for industrial action, which is expected to conclude at the end of May.

Depending on the vote, this could result in the first strike in the UK steel industry in more than 30 years.

Tata Steel fell 2 per cent in Mumbai in advance of the results.