The five main channels top Sky's UK programme guide

BBC One and BBC Two are currently the top two channels viewers see on Sky Digital's programme guide.

But the BBC is ending a deal with Sky Digital to encrypt its services next month, although Sky Digital subscribers will still be able to receive the channels.

BSkyB says the BBC must pay for the technical service required to let it keep the top slots under the new arrangement.

The BBC says any move from the top two slots would confuse viewers, and has called in the Independent Television Commission to adjudicate.

ITC regulations say "due prominence" must be given to public service channels such as BBC One and BBC Two.

'Most-watched'

A BBC spokesman said: "BBC One and BBC Two are among the most watched channels in multi-channel homes and Sky will be doing their customers no service by moving them down the list.

"Sky customers expect to see us on channels 101 and 102 and now they might have to scroll down the list to find us."

The corporation believes moving BBC One and BBC Two would be a breach of the 1996 Broadcasting Act, which guarantees the channels a prominent spot on the satellite service's programme guide.

The BBC will be broadcasting its channels from a different satellite from 30 May, which it says means it will not have to pay Sky to encrypt its channels so they can only be seen in the UK.

The satellite the BBC currently uses transmits to most of western Europe, while the one the BBC is moving to is directed at just the UK and Ireland.

Regional split

But the top listings slots on the new satellite are already occupied by Irish network RTE, and the BBC would have to pay to split it to appear at the top of the Electronic Programme Guide (EPG) in the UK.

"The continued presence of the BBC channels in EPG slots 101 and 102 in the UK will involve the provision of a technical service known as conditional access regionalisation," a Sky spokesman said.

"Sky provides such services to broadcasters on regulated terms, but it doesn't provide them for free."