Rural Scotland and Wales and the Lake District still have Britain’s slowest average connection speeds, but broadband users in Tower Hamlets, Westminster, Tunbridge Wells and Canterbury all put up with speeds of 11.5Mbps or less, according to analysis by Which?.

In comparison, commuter borough Broxbourne enjoys speeds of 32.5Mbps on average which is considered superfast by both the Government (over 24Mbps) and Ofcom (over 30Mbps).

To put this into context, downloading a film in Canterbury would take around three times longer than it would in Broxbourne.

The UK Government has pledged to ensure a bare minimum connection speed of 10Mbps per second across England. There are additional schemes in place in Wales and Scotland.

The Which? data suggests residents in 15 UK local authority are failing to access these speeds.. They might find it hard to use online banking or streaming services like Netflix or BBC iPlayer.

Users in the Orkney Islands put up with the slowest internet connection, with average speeds of just 3Mbps.

Alex Neill, Which? managing director of home products and services, said: “Having a good broadband connection is a basic requirement for many important everyday tasks, so it is unacceptable that millions of people around the country are still struggling to get what they need.

“The Government and the regulator must now press ahead with plans to provide a bare minimum connection speed of 10 Megabits in every household and make sure that no one is at a disadvantage because of where they live.”

Switch to a better deal

Separate research by the consumer group found some households with sluggish broadband connections could get faster speeds – and save hundreds of pounds a year – by switching to a better package.

Many people do not take up the fastest service available in their area, according to the regulator, Ofcom

Only 45% of premises were signed up to superfast broadband despite the service being available to more than double that number, it said.