Seventeen European countries - including the UK - are facing legal action to force them to open their national energy markets competition.
The European Commission crackdown follows the failure of a majority of member states to comply with EU rules and break up monopoly energy sectors artificially propping up gas and electricity prices.
The move was welcomed by UK trade and industry secretary Alan Johnson who said liberal energy markets across the continent would save UK consumers up to #10 billion a year in lower gas and electricity prices.
A Commission report last November praised British, Dutch and Danish efforts to meet the demands of fair and open energy markets by implementing EU energy market liberalisation rules.
But the UK finds itself included in the list of nations announced this afternoon as targeted for court action because of a technicality over the setting up of an electricity "interconnector" between Britain and Northern Ireland.
Officials are irritated at the UK's inclusion when the country is recognised as having an open energy sector.
One government spokesman said: "The Commission has identified a minor infringement in the UK.
"This concerns the way capacity was allocated on the Moyle interconnector before the Directives (on market opening) were agreed."