British telco Virgin Media is facing a £50,000 financial penalty after spamming more than 400,000 opted-out customers.

A customer complained to the Information Commissioner's Office (ICO) about receiving the spam -- but that was enough to spur the regulator into investigating.

In a message disguised as a routine communication about tariff prices, Virgin told 451,217 recipients it knew full well they'd opted out of marketing emails but wanted them to opt back in.

Unfortunately, that is not how the spam opt out rules work. If you are opted out, a company cannot spam you to opt in. In fact if you have opted out, the company should have destroyed your data.

When the ICO asked Virgin why it did this thing, the telco said the 451,000 recipients had opted out of being spammed more than a year ago, and "might have changed their marketing preferences".

Only 6,500 customers decided to opt back into receiving marketing emails as a result of the mailshot, the ICO said this wasn't enough to ignore regulation 22 of the Privacy and Electronic Communications (EC Directive) Regulations 2003.

The fact that Virgin Media had the potential for financial gain from its breach of the regulation (by signing up more clients to direct marketing) is an aggravating factor, not a defence, the watchdog growled.