The shutdown of Escondida, which accounts for 8 per cent of the world’s copper output, pushed up the price of the red metal by $180 per tonne to $7,470 on the London Metal Exchange. Chile’s President, Michelle Bachelet, called for talks to resume between the miner and the unions, who are demanding a substantial pay rise and bonuses to reflect the huge profits earned from high copper prices.

In London, the price of nickel gained $300 per tonne as volumes in LME warehouses dwindled further. China’s largest nickel producer expressed concern that the nickel market was being distorted by speculators and urged the LME to improve regulation.

“The LME is no longer a place for fair dealing metals but a paradise of speculation,” said Li Yongjun, chairman of Jinchuan Group, the largest nickel producer in China.

Nickel reached a record high of $29,200 per tonne in the forward market as stocks plummeted to less than a day’s supply. The premium for cash nickel over three-month delivery widened to almost $5,000 per tonne, prompting the LME to introduce emergency rules on Wednesday to allow short sellers to escape the squeeze.

BHP’s tough stance with the Escondida strikers may be supported by the Chilean Government, reckoned some analysts, as Escondida pays its workforce the highest mining wages in Chile, and the state copper company, Codelco, will be anxious to avoid a high settlement with its own workers. “They won’t want to see BHP set a precedent and stoke higher wage claims at Codelco,” said Robin Bhar, metals strategist at UBS.

BHP said that it had shut the mine for safety reasons but Pedro Marin, a spokesman for the strikers, accused BHP of trying to scare the workforce. “This is illegal pressure,” he said.

BHP would not put a timescale on the stoppage, which follows 12 days of reduced output since the strike began. BHP is offering a 3 per cent pay rise plus a bonus of $16,000 (£8,500) to each of the mine’s 2,900 workers. The union, which represents 2,050 miners, is demanding a 13 per cent pay increase and a $30,000 bonus.

The global mining industry is suffering a wave of labour unrest as workers seek to extract their share of exceptional profits from high metal prices.

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