E.On cut its gas prices by 5.1% on 1 February, Scottish Power will cut its gas tariff by 5.4% on 15 March, and SSE will reduce its gas prices by 5.3% from 29 March.
Npower said the fall would benefit about 1.2 million customers, with an average annual saving of £32 a year for customers on a standard domestic gas tariff.
British Energy Minister Amber Rudd commented: “Energy suppliers must give consumers a fair deal and that’s why I’ve been calling on energy companies to put their customers first and pass on savings to them.
“Npower is now the fourth of the Big Six to take a step in the right direction by dropping its standard gas price and I urge other suppliers to follow suit.
“The Government is also taking action to keep bills low by making it easier and quicker to switch, rolling out smart meters to every home and business, and increasing competition in the energy market”.