At least $74 million has been spent on marketing, lawyers and consultants for the privatisation of NSW electricity network businesses in what the state opposition has criticised as a "feeding frenzy" for the big end of town.

Treasury figures confirm that the biggest winner from the transactions was consultancy Ernst and Young, which reaped $24.5 million for providing financial, accounting and tax advice to the government.

Ernst and Young wrote the report used by the then Baird government to bolster its argument for partially privatising the NSW electricity network.

The report concluded that customers have paid lower charges in Victoria and South Australia after privatisation.