BRITISH Telecom is to spend £4.6 bn buying the remaining stake in German phone operator Viag Interkom, it revealed last night.

BT, which already owns a 45 per cent stake in the fixed and mobile phone operator, is to buy a further 45 per cent stake held by utilities group E.ON for a fee estimated at 7.25 billion euros, equivalent to £4.6bn, completing an option agreement announced last year.

In December, BT bought a ten per cent stake in Viag from Norwegian telecoms firm Telenor in a deal worth 1.61 billion euros, or £1bn, which is due to be completed later this month.

Once both deals are completed, BT will become the sole owner of Viag, which is the smallest of Germany's four mobile phone operators with a current customer base of around 3.5 million users.

A BT spokesman said yesterday: ''The purchase of E-ON's stake in Viag Interkom will give us full ownership of a major and innovative player in the German telecommunications market, which is the largest national communications market in Europe.'