The North's main gas supplier is eyeing up Bord Gais assets earmarked for sale.
Phoenix’s parent company Terra Firma said it will seriously consider bidding for the semi-state’s supply or energy businesses if it is broken up.
The Government is examining options for a sell-off of state assets drawn up by economist Colm McCarthy to pay for the multi-billion euro banking crisis and borrowing.
Phoenix said moving into the Irish market by buying Bord Gais assets would be a natural fit for its business.
“We are interested in any and all energy assets,” a company spokesman said. “The potential purchase of further energy assets across the island would represent a natural fit and an expansion opportunity.
“To this end any Bord Gais assets that become available for acquisition would be very seriously considered.”
The McCarthy review group on state assets called for Bord Gais and ESB to be broken up.
It said the state-owned gas company should sell off its power generation assets, such as the Whitegate plant in Cork, and the supply and distribution business.
ESB was warned it should also be broken up and its electricity supply and power production businesses sold, including Northern Ireland Electricity, a deal which it only finalised late last year.
McCarthy, however, has warned against a "fire sale" of assets.
Private equity giant Terra Firma has made inquiries over the possible sell-offs but management have been told that there will not be any talks until specialist government advisers have been appointed.
The company is examining all options from electricity production to renewable energy.
“Terra Firma believes the recovering Irish economy will provide further opportunities to invest in Ireland and assist in renewed growth,” the spokesman added.
Phoenix has invested more than £400m (€453m) in the Irish energy market since 1996. Last month Terra Firma, through their renewable energy company Infinis, bought the Slieve Divena windfarm in Co Tyrone from Scottish and Southern Energy.