Mercury Telecom has been pulled up over direct mail sent to businesses in the form of an invoice.

Text in the middle of the mailing stated: 'Invoice summary for call charges ... service charges ... VAT at 17.5 per cent' with the charge for each service displayed as '£0.00'.

Text at the bottom of the mailing stated: 'Thank you for paying by direct debit. Payment will be collected on or after 3rd September 2007.'

A single complaint to the Advertising Standards Authority (ASA) came from someone who was not a Mercury Telecom customer.

The challenge centred on whether the mailing was misleading because it did not make clear that it was advertising material.

Mercury Telecom responded by claiming that the direct mailing was meant to show the benefit of free line rental for those using its service.

"Mercury said that the mailing was followed up two days later with a letter explaining the nature of the first contact," the ASA ruling stated.

"Mercury said that it would not be using that marketing approach again and apologised if consumers had found the ad confusing or misleading."

The ASA upheld the complaint, noting that it breached the CAP Code on 'honesty', 'truthfulness' and 'recognising marketing communications and identifying marketers'.

"We welcomed Mercury's assurance that the direct mailing would not be used again in the future," the ASA declared.

"Nevertheless, because we considered that the invoice had not been clearly identified as advertising material anywhere on the mailing, we concluded that the ad was misleading."