The government said on Monday it would cut some green levies paid by energy companies so they could cut prices.
EE, the market No. 1 with roughly 27 million subscribers, Vodafone, Three and Virgin Media said they would allow customers to break contracts without penalty if their tariffs were raised mid-contract, a Department of Culture and Media statement said.
No. 2 mobile operator O2, with about 23 million subscribers, said it was still in talks with Britain's government about the proposals.
O2 said in a statement, "We need clarity on what the guidance means for us and our customers before we can sign up to all the commitments referred to by Government."
It was not clear when the proposals on mobile phone charges - among some of the lowest in Europe - would be introduced, but the government said it was aiming for the liability cap to be in place from spring next year.
The government said the four mobile phone operators as well as fixed-line providers BT, Sky and TalkTalk had also pledged to support European Commission-led plans to eliminate roaming charges within Europe by 2016.
When the plans were unveiled in September, the commission said they would foster a cross-border market for telecoms services and spur investment in networks, but mobile operators say they would erode short-term profits.
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