SANTIAGO, Jan 21 (Reuters) - A union representing workers at BHP's Escondida mine in Chile, the world's largest copper mine, said on Friday the firm had been erratic and irresponsible as COVID-19 infections have risen among the workforce.

"We consider that the company has been erratic, dismissive and irresponsible in the responses it has given us, emphatically denying, on the afternoon of January 14, that there was an outbreak of COVID-19," the union said in a statement.

The mining company reported earlier this week there were 312 cases affecting workers and contractors, who have been quarantined, but declined to offer details on the possible impact on its operations.

Escondida declined to comment on the union's statements.

Chile is experiencing a record surge in COVID-19 cases driven by the highly contagious Omicron variant. Deaths, however, have remained low as Chile has one of the highest vaccination rates in the world.

Chile is also the world's top producer of copper.

The union said Escondida had "eliminated and dangerously relaxed protocols and control measures," weakening the company's ability to trace the origin of cases.

The company said in an earlier statement it had applied rigorous measures in line with the requirements of the health authority and said 90% of its workforce has been fully vaccinated against the virus. (Reporting by Fabián Andrés Cambero; Writing by Carolina Pulice; Editing by Chris Reese)