TalkTalk has slammed BT for calling on rival telecoms companies to lower the call charges incurred when phoning mobile phones saying it's "still loads cheaper" than its rival.

Earlier this week, BT announced it has slashed the cost of calling a mobile phone from a BT landline in the evening to 5.3p per minute, that's nearly a quarter less than previous charges of 7p per minute. Meanwhile, during the day, the cost will fall by 13 percent to 11.3p from 13p per minute. The telecoms company said the reductions are simply BT passing on the savings after Ofcom decided to slash the termination charges levied by some mobile operators when Brits called customers on their networks.

"We are passing on Ofcom's reduction. In the mean time, we are naming and shaming Sky, TalkTalk and Virgin Media who will be charging so much more than BT for calling mobiles," said John Petter, managing director of consumer products, at BT said.

"We call upon them to give what over 160,000 members of the British public, 65 public sector organisations, unions and consumer groups and 262 MPs asked for in the Terminate the Rate Campaign: lower charges for landline calls to mobiles."

However, TalkTalk said it more than matches BT's call charges, "in fact, we've been offering much cheaper rates for some time and are still loads cheaper than BT even after its latest price changes".

"The reason for BT's underwhelming change to its prices is because Ofcom has demanded they be cut. Yet we reduced our prices back in October last year, even before we knew what level Ofcom would set. And, as our sums demonstrate, we've gone much further too," said the ISP in a blog.

TalkTalk believes a customer spending 100 minutes a month on the phone to mobiles will save £175 over the course of a year with its 100 Mobile Minutes Boost, which costs £3 per month. Meanwhile, a heavier user, using all of their 500 mobile minutes booster, priced at £5 per month, would save an enormous £993 a year. Even someone using just 200 of their 500 monthly mobile minutes would save £361 over the course of a year compared to BT.

"That's a saving not to be sniffed at – and gives you some idea of how much BT is over-egging how good value its new call rates to mobile phones are," the telecoms company said.

"So if you're a BT customer who calls mobiles a lot – and, let's face it, most of us do nowadays – why not ask BT why it's too mean to match our prices?"

However, a BT spokesperson said TalkTalk is comparing apples with pears by comparing its landline-to-mobile bolt-on with BT's standard ppm rates.

"TalkTalk's standard pence per minute rates are higher than BT's and to take advantage of the rates TalkTalk mentions, customers have to spend £5 per month. TalkTalk's bolt-on is opt in; our rate cut is automatic.  Only a tiny percentage of TalkTalk's millions of customers will see the deal and benefit."

Meanwhile, Virgin Media said it already offers "great value phone bundles to all of our customers and as the first home phone provider to offer free calls to Virgin Mobiles, Virgin Media families are already saving hundreds of pounds a year".

"We're looking forward to introducing even more market-leading mobile and home phone offers in the future," a spokesperson added.