The television campaign by CHI & Partners launches tonight. It claims British Gas now has the cheapest electricity prices in all regions.
British Gas's 5% cut in its electricity prices are coming into action with immediate effect, while the 5% cut to EDF Energy's gas tariff will not occur until 7 February.
The television campaign has been in planning for the past few weeks and is not an immediate reaction to yesterday's announcement by EDF Energy.
Energy suppliers have scope for cutting prices because of the mild winter in the UK, which resulted in increased stocks of gas with a knock-on effect on wholesale prices.
EDF Energy was the firm that held its prices lowest for longest last year when all the "big six" energy firms hiked their prices.
In contrast, British Gas was the first to announce the prices hikes, which resulted in it shedding 100,000 customers, according to analysts.
EDF Energy has hinted it is considering its own campaign to publicise its price cuts.
A spokesman said: "We are currently considering our options regarding how best to communicate [yesterday's] announcement of a 5% decrease in gas prices through advertising."
Follow Matthew Chapman at @mattchapmanUK