A Manhattan judge has blocked the municipal hospital system from laying off 150 carpenters, electricians and laborers — dealing a blow to its financial-reorganization plan, officials said yesterday.

Supreme Court Justice Alice Schlesinger ruled last Wednesday that the Health and Hospitals Corp. acted in an “arbitrary and capricious” manner when it handed out pink slips in mid-September as part of a larger plan to contain spending.

HHC faces a $1.2 billion deficit and wants to reduce its workforce by 3,700 over the next four years. The city is planning an appeal.