Broadband services are getting faster in Britain but the gap is growing between advertised speeds and actual download rates, telecoms regulator Ofcom said on Tuesday.

Research published by the watchdog showed typical fixed-line residential broadband speeds increased by 27 percent in the year to April from 4.1 to 5.2 Mbit/second as firms acted to offer higher speed packages.

But it said most consumers were actually receiving less than half of advertised speeds and that the trend was getting worse.

Ofcom Chief Executive Ed Richards said there was scope for a step change improvement in the quality of the country's infrastructure.

Actual speeds are often much lower than many of the advertised speeds, which makes it essential that consumers are given information which is as accurate as possible at the point of sale, he said, unveiling a new code of practice aimed at empowering consumers.

In April 2009, some 58 percent of average advertised up to speeds of 7.1 Mbit/s were achieved versus 45 percent of 11.5 Mbit/s up to speeds in May 2010.

Under the new code, customers will be able to cancel broadband contracts if internet speeds are significantly below the estimate provided by their providers.

We are delighted that all major ISPs have signed up which is a major step forward, Richards said.

Ofcom said the big disparities in speed were often caused by services being delivered over copper lines which were simply designed for phone calls.

It said long and poor quality lines as well as electrical interference would significantly affect speeds.

The regulator also said cable broadband services delivered significantly faster download speeds than comparable Digital Subscriber Line (DSL) services.

(Reporting by Stefano Ambrogi; Editing by Steve Addison)