TORONTO -- The Canadian Union of Public Employees is suing the Ontario government over the sale of Hydro One, the province's electricity transmission monopoly.

CUPE president Fred Hahn says the union's lawyers served the Ministry of the Attorney General on Tuesday with notice of intent to sue, but the government said today it still was "not aware of any action from CUPE."

CUPE claims the Liberals inappropriately mixed government and party business by holding fundraisers with cabinet ministers for up $10,000 a plate, including one attended by bankers who profited from the sale of Hydro One shares.

The Liberals plan to sell up to 60 per cent of the huge utility, which also serves as a local electricity distribution company for 1.3 million homes, mainly in remote and rural parts of Ontario.

The province raised $3.2 billion from selling 30 per cent of Hydro One so far, but CUPE hopes its lawsuit will stop the sale of any more shares.

The Liberals say the money raised from the privatization of Hydro One is needed to fund public transit and infrastructure projects and to pay down debt.

Hahn says CUPE successfully sued the previous Progressive Conservative government to stop its plan to sell Ontario Hydro, which the Tories broke up into several different companies, including Ontario Power Generation and Hydro One.

"The principal reason for filing this suit is to stop them from selling additional shares in our hydro system," he said.