Around 750 contractual workers commissioned by a handling agency at the Haldia port have ceased work since Thursday, stalling unloading operations from at least two large vessels.

The “indefinite strike” has been called by the trade union wing of Trinamul to which most workers are aligned.

The move raised brows at Haldia port, where companies have been assured several times in recent years of chief minister Mamata Banerjee’s aversion to labour strikes.

A source in the trade union wing of Trinamul said the immediate trigger for the strike was longstanding demands of workers by contractor Five Star Shipping Corporation, such as unpaid provident fund and ESI dues.

After the mobile harbour crane unloading of two vessels at berths 8 and 4B, laden with petro coke and rocks, respectively, were over on Thursday, workers refused to pitch in manually.

“On Friday, a director of handling agency Ripley and Co. sent a letter to Five Star Shipping Corporation, who had hired the contract labourers, asking for immediate resolution of the crisis,” said a source at the port.

Five Star Shipping Corporation, however, blamed Ripley for not clearing dues over the last five years. Director of Five Star Shipping Corporation, Sheikh Ashraf, said Ripley owed them Rs 8.56 crore, and hence PF/ ESI dues of contract workers remained unpaid. “Ripley has promised to make some payment on Monday. If it happens, we will update the PF and ESI dues of workers and request them to resume work from Monday.”

East Midnapore unit chief of INTTUC, Dibyendu Ray said the workers’ demands were valid but the government did not support such a strike. He promised to look into the issue on a priority basis.

Ripley has raised the issue with waterways minister Saumen Mahapatra and INTTUC state president Ritabrata Banerjee.