Ofcom has been conducting mystery shopping excursions into the world of broadband, to check which providers are complying with its Voluntary Code of Practice on Broadband Speeds.
The organisation notes that while the information supplied to potential customers by ISPs has improved, there's still work to be done, particularly in the case of BT and TalkTalk.
Ofcom found that in 93 per cent of its telephone-based enquiries, a speed estimate was given - and in 72 per cent, that estimate was delivered in the form of a range.
However, Ofcom's code stipulates that an estimate should be volunteered as early as possible in the sales call - yet some ISPs needed to be asked before they gave up any line speed estimation. Forty-one per cent of mystery shoppers needed to ask, in fact.
The best ISPs who proved most likely to offer an estimated speed without any prompting included Karoo, which managed a 76 per cent success rate, followed by Sky on 72 per cent. Plusnet was next on 67 per cent.
At the bottom end of the table was BT on 48 per cent, and TalkTalk on 47 per cent. Ofcom has had a quiet word with both of these providers, who have agreed to adjust their staff training and sales guidelines to improve this aspect of service.
Claudio Pollack, Ofcom's Consumer Group Director, said: "It is vital that as the choice of broadband services expands, UK consumers get the best possible information when choosing a broadband provider. Our mystery shopping shows that, while consumer information about broadband speeds has improved in important areas, there is still more to be done.
"We are working with internet providers to improve information that consumers receive when they sign up to a new service and will continue to monitor this area closely."