ZURICH, May 19 (Reuters) - Swiss voters easily approved on Sunday a shake-up of the country's corporate tax system, heading off what its finance minister had called an existential threat to Switzerland's role as a business hub, projections for Swiss broadcaster SRF showed.

The projections from the gfs.bern polling outfit saw the measure passing in the binding referendum by a 66-34 percent margin.

The vote on tax reform and pension finance defuses a long-running row over favourable Swiss tax rates for multinational corporations. Acceptance was vital to prevent the country being branded a low-tax pariah, Finance Minister Ueli Maurer has said. (Reporting by Michael Shields; Editing by Alison Williams)