Greek lawmakers approved a controversial breakup and privatisation of the country's main electricity provider on Wednesday.
The law to break up the state-owned Public Power Corporation (PPC) by 2015 was approved by the government majority amid protests outside parliament.
The move is part of a privatisation drive required by EU states in return for multi-billion euro bailout to save the country from bankruptcy.
The new, scaled-down private company will control a 30-percent share of PPC's extensive production resources, including mines and hydroelectric, natural gas and lignite-fired electricity generation plants.
The Greek state has also pledged to sell off 17 percent of its 51 percent stake in PPC. Employee pension funds hold another 3.8 percent.
The liberalisation of Greece's energy market, which has been dominated by state-controlled PPC for decades, is a key requirement for continued loan support from the country's creditors, the EU and IMF.
But the move has been strongly criticised by unions and opposition parties.
Main opposition leader Alexis Tsipras of the radical leftist Syriza party has called PPC's breakup a "national crime" and is mustering support for a referendum against the decision.
"You took over a state and will hand back a colony, a colony of big private interests," Tsipras said in parliament, accusing the government of selling valuable public enterprises for "a pittance".
"The law to further liberalise the energy market (will lead to) electricity price hikes... and wage cuts for staff," Communist party chief Dimitris Koutsoumbas told protesters near parliament.