Ministers clashed with unions as Francis Maude said mass public sector strikes next week could cost the economy £500m and lead to job losses. Mr Maude, the Cabinet Office Minister, explained the Treasury had made the estimate based on lower output in the public and private sector. More than two million workers are expected to strike on November 30 over changes to public sector pensions. Mark Serwotka, PCS Union head, said the government was making “false” claims about the pensions.