Ofcom has urged UK consumers to report any broadband and phone 'bill shocks' they have experienced in the last 12 months.
The communications regulator claims that up to five per cent of landline customers have experienced unexpectedly high bills during the last year.
Common reasons for high bills were making calls not included in a broadband bundle (19 per cent), phoning 0845/0870 numbers (16 per cent) and exceeding bundle tariffs (15 per cent).
Ofcom is seeking feedback from consumers who have been affected, as it ponders whether to take action to create additional protections.
At present, all broadband consumers must be provided with clear and transparent information about their contract and bills.
The regulator is seeking to establish whether internet service providers are meeting their obligations in this respect.
Ofcom receives 450 telecoms complaints every day, relating to home phone, mobile and broadband services.