The Advertising Standards Authority has warned internet service providers they cannot claim to offer free access to the web if any part of their service carries a charge.

The ASA has upheld complaints about a BT SurfTime national press and poster campaign, ruling that it was misleading.

The ASA said it received a complaint from AOL Bertelsmann that the tariffs shown in the BT ads implied misleadingly that both were available from all ISPs, and another complaint from a member of the public about the non-availability of SurfTime to existing BT internet customers.

A mail-shot for NTL's free ISP, ntlworld, attracted 167 complaints after applicants had to wait several months for the service.