T-MOBILE and mmO2, Britain’s third and fourth-largest mobile phone groups, will halve the cost of their call tariffs for new billed customers from today, in an attempt to head off competition from 3, their rival owned by Hutchison Whampoa of Hong Kong.

Carphone Warehouse, Europe’s largest mobile phone retailer, said in a statement that mmO2 and T-Mobile would be offering mobile phones for contract customers at “pretty much half the price” of the operators’ current tariffs. Carphone claimed that the move by the two groups had been triggered after 3 dramatically cut its own trariffs in June.

Andrew Harrison, chief executive of Carphone Warehouse, said: “Since 3 slashed their prices in June, their sales have been flying. The networks are kicking back.”

Mr Harrison claimed that customers were attracted by 3’s “cheap talk” strategies. The “Videotalk 500” plan offers 500 free minutes to any network at any time for £25 a month, almost half the price of its nearest rival for comparable talk time.

But as of today, mobile phone users will be able to buy T-Mobile and mmO2 phone plans on a similar basis. T-Mobile will offer 500 inclusive off-peak minutes across networks for just £20 per month. MmO2 is offering the same through all retailers, plus 100 free texts, for £25 a month.

T-Mobile claimed last night that they had been offering the tariff available to mobile retailers yesterday on their website for several weeks, but that the terms described on their site which were different, were inaccurate.

MmO2 denied yesterday that the new strategy was an attempt to combat 3’s cheap deals, claiming its new tariff was an extension of its existing talk plans.