Overall, advertised speeds from the 12 biggest providers across all types of packages up to 100 Mbps dropped by 15 percent. One company, TalkTalk, completely eliminated advertised speed claims and another (Vodafone) has removed the word "Fiber" from two offers. Only Virgin Media, which made a point of knocking rivals over dubious claims, increased its advertised speeds.

The ASA launched the new rules after finding that British broadband users were paying for internet packages that were 51 percent slower than advertised. It created a similar rule last year that forced providers to include phone line rentals in advertised ADSL broadband prices.

In the US, meanwhile, internet can't be advertised as "broadband" unless it offers at least 25 Mbps download and 3 Mbps upload speeds. The FCC, under industry-friendly chairman Ajit Pai, was thinking of rolling back that rule, but thankfully, backed off.