The move follows an internal pricing review that has enabled npower to undercut Scottish market leader Scottish Power on its home territory.
Npower head of customer marketing Kevin Peake said: 'Traditionally, Scottish Power has had little competition on its home turf. But we're determined to change that and are looking to build recognition of the npower brand and springboard our sales activity.'
Citigate beat Trimedia Communications, Consolidated Communications and Euro RSCG Leedex to land the account.
Npower hired Ptarmigan to manage its consumer PR in England in February (PRWeek, 18 February).