A split has emerged in NSW Labor over policies to tackle inequality just a week after federal opposition leader Bill Shorten declared that doing so would be "a defining mission" for a government led by him.

NSW Labor's economic policy committee, controlled by the right faction, has rejected 13 of 17 inequality-related motions put to this weekend's annual state conference at Sydney Town Hall by the left, prompting accusations it is "gutting" attempts to fight the problem.

The rejected motions include inserting a declaration of the party's determination to fight inequality in the state Labor platform and implementing an annual report on the state of inequality in NSW.

The committee has rejected a motion to add to the state platform support for the Buffett rule – the principle that a minimum level of tax should be paid by all, as advocated by billionaire businessman Warren Buffett – despite it appearing in the national Labor platform.