In a trading update for the 13 weeks to September 30, the retailer said that the 'strong' results were a result of its total customer numbers increasing 34 per cent to 2.4 million.
However, it also revealed that the recruitment of more call centre staff to deal with the 'unprecedented' demand for fixed-line business Talk Talk's free broadband offer had meant costs for the operation rose by£20 million to£70 million.
Carphone Warehouse chief executive Charles Dunstone said that, although 200,000 of 625,000 customers remained unconnected to broadband, the additional costs would not impact on figures for the year to March 2008.
He added: 'Our underlying performance for the first half has been ahead of our expectations and we expect interim pre-tax profits to be up 50 per cent year on year.'
Carphone Warehouse opened 66 stores in the second quarter, taking its portfolio to 1,921.