Energy giant British Gas has announced a price freeze for more than six million customers on standard tariffs over the winter.
The UK's biggest energy supplier will keep its gas and electricity standard variable tariffs on hold until at least March.
British Gas said it would provide "peace of mind" for standard variable customers.
The move follows SSE's price freeze last month until at least April and comes amid pressure on energy firms to treat loyal customers fairly.
A report recently accused Britain's Big Six suppliers of overcharging families and making six times the profit they admit to publicly.
British Gas also said it will ensure all existing and new customers can access its best deals from next year, and will launch an energy health check for standard variable customers to make sure they are on the right tariff.
In a Christmas message to customers, British Gas chief executive Mark Hodges said: "The commitments we've made today show British Gas has been thinking hard about ways to improve how the energy market works for all our customers, and is taking tangible action.
"You will see us doing even more in the coming months."
British Gas added that its standard variable tariff was already the second cheapest in the market.
It has also launched a deal allowing households to fix energy prices for three winters, until March 2019.
Business Secretary Greg Clark recently met energy company representatives to discuss concerns that they are abusing customer loyalty following a report commissioned by industry lobby group Energy UK.
The report found the cost of supplying a home with gas and electricity "falls well below" what households pay, averaging around £844 while families pay as much as £1,172 with some suppliers - giving profit margins of up to 28%.
But wholesale energy prices have been rising, leading to the collapse of smaller provider GB Energy earlier this week.
It had recently hiked tariffs by as much as a third, while other small suppliers have also had to increase prices.
GB Energy's 160,000 customers have since been taken on by Co-operative Energy, which is honouring outstanding credit balances and tariffs for GB's customers.