TORONTO - Ontario is fighting back against federal Conservatives who say Ottawa had nothing to do with the province's decision to move ahead with tax harmonization.

Ontario Finance Minister Dwight Duncan says some Tories are trying to have it both ways by encouraging provinces to move to a single sales tax, then speaking out against it when their constituents complain.

He says Ottawa gave him "4.3 billion dollars of reasons" to move ahead with tax harmonization - referring to the amount of federal cash Ontario will receive to ease the transition.

The Prime Minister's Office and several federal Tories have recently distanced themselves from the contentious plan to merge provincial sales taxes with the federal GST, which will hike the cost of many items currently exempt from the provincial levy.

They say Ottawa had nothing to do with the decision even though it's kicking in billions of dollars to make it happen in both Ontario and British Columbia.

Under its deal with federal Finance Minister Jim Flaherty, B.C. will get $1.6 billion in cash to move to a single tax.