"We are currently in the process of fulfilling all regulatory requirements in advance of entering the GB energy market later in 2017," a spokesman said, declining to give further details.

The state-owned company is Ireland's incumbent electricity provider and supplies 2.3 million customers in its home market.

Its foray into the British energy retail market follows a string of other foreign energy companies which have set up British retail units, such as France's Engie (>> Engie) and Sweden's Vattenfall [VATN.UL].

Britain's energy retail market is highly competitive, with more than 50 suppliers offering to bring electricity and gas through various tariffs to households and commercial end consumers.

The sector's 'Big Six' suppliers have come under pressure in the past few years after anti-trust regulator the CMA found that many customers placed on the most expensive tariffs had been overcharged 1.4 billion pounds a year between 2012 and 2015.

The 'Big Six' energy companies are Centrica's (>> Centrica) British Gas, SSE (>> Scottish and Southern Energy), Iberdrola's (>> Iberdrola) Scottish Power, EDF Energy (>> Electricité de France), E.ON (>> E.ON) and Innogy's (>> Innogy SE) npower.

Britain's regulator has since ordered suppliers to reduce the maximum tariffs for customers on prepayment meters and the government launched a review this month into how best to reduce long-term energy bills.

(Reporting by Karolin Schaps. Editing by Jane Merriman)