The NSW government has refused to release the names of corporations enjoying the greater part of its $1.8 billion in tax breaks lest they be exposed to "harsh public criticism" and scrutiny, documents released under freedom of information reveal.

In 2016 then-Treasurer Gladys Berejiklian announced a $400 million a year slashing of taxes on the transfer of shares between private companies and trusts, business mortgages and intangible assets such as intellectual property. Over four years they are expected to cost $1.8 billion in revenue.

NSW Premier Gladys Berejiklian was making good on a deal that dated back to John Howard's GST. Credit:AAP

But the state government is refusing to release a list of the businesses that will benefit the most from the tax cuts, likely to include commercial property developers, to spare singling them out for public scrutiny.

But Labor argues information about where the government is directing money through tax breaks is fundamental to judging a government's priorities.