(TNS)BOSTON — A proposal to cut Massachusetts’ personal income tax to 4% would cost the state government an estimated $5 billion a year in lost revenue, according to a new report from a left-leaning policy group, which warns the move would trigger deep cuts in public services. But the Massachusetts Budget and Policy Center says cutting the income tax rate would mean an estimated $5 billion less revenue for the state government. A recent report by the coalition cited analysis showing that lowering the Massachusetts income tax rate would deliver long-term benefits to the state’s economic growth. To be sure, Massachusetts voters overwhelmingly approved a ballot question in 2000 to cut the personal income tax rate to 5%. Two years after its passage, however, the Legislature outraged supporters of the rollback by freezing the personal income tax at 5.3% to plug budget shortfalls.