New designs are driving sales

In the 13 weeks to 25 September, the firm saw connections grow by 25% on the same period a year ago to 1.55 million.

The company added that its landline TalkTalk service had added 137,000 customers in the quarter, and now had 648,000 users in the UK.

"Trading over the first half has been ahead of our expectations," said chief executive Charles Dunstone.

"The mobile market remains buoyant and we have achieved further good growth in both subscription and pre-pay connections."

Subscription connections rose by 18.3% compared with a year ago while pre-pay connections grew by 29.8%.

Mr Dunstone added that he expected half-year pre-tax profits to be "at least �27m, after significant investment in TalkTalk marketing costs".

The firm said these marketing costs meant the TalkTalk business - which recently launched in Spain and Germany - was expected to chalk up a �6m interim loss.