Kent and Sussex are the UK's two worst counties for broadband speeds.
Over half of Britain's top 20 broadband blackspots are in the south of England, according to research from Uswitch.com. Kent and Sussex have three towns each on the list.
Cranbrook in Kent, had the slowest broadband speeds in the country. The town of around 7,000 residents has an average download speed of just 1.32Mbps, five times slower than the national average and 14 times slower than the UK's fastest town, Leamington Spa, which has an average speed of 18.87Mbps.
The survey's findings - based on almost 400,000 speed tests conducted between May and June 2011 - came just days after the government's announcement that it will be investing £363m to improve broadband speeds to homes and businesses across England and Scotland.
Ernest Doku, technology expert at Uswitch.com, said thousands of homes are making do with download speeds well below the national average. "Fast broadband speeds should be available to everyone, not just for those people living in heavily urbanised areas."
"Intense competition among broadband providers means that companies such as BT and Virgin Media are rolling out super-fast fibre optic networks as a priority."