"Citi is in the process of expanding power and gas trading in Europe. We have made a number of hires in sales and trading since the autumn of last year," the spokesman said.

Citi's London power and gas desk currently employs 10 people, up from seven before the expansion, the spokesman said.

Several large investment banks have cut staff in their European power and gas trading divisions or shut them down completely over the past couple of years in response to tighter regulation and reduced opportunities for arbitration.

Earlier in January, Bank of America Merrill Lynch closed its European power and gas desk. Deutsche Bank shut power and gas trading in December 2012.

Some utilities have also cut power and gas trading staff in Europe due to financial pressures.

(Reporting by Nina Chestney; editing by Jane Baird)