Telecoms giant BT today announced it is to step up the roll-out of its superfast broadband, making it available to an additional one million homes and businesses by the end of next year.

The company said it will open a further 66 exchanges across the country that support fibre optic cables as part of a £2.5 billion programme to provide quicker broadband services for two-thirds of homes in the UK.

Most of the new exchanges announced today will "go live" in 2012 although some will be up and running by the end of this year.

Some five million homes in the UK will have access to superfast broadband by the end of this month, in a development BT described as a significant milestone.

Today's announcement, which comes on top of previously planned investments in its network, means BT is on track to hit its target of reaching 10 million homes with fibre-optic cables by the end of 2012 and more than two-thirds of the UK homes by the end of 2015.

The fibre-optic cables support download speeds of up to 40 megabytes per second, which is easily fast enough to allow users to watch high definition television over the internet. They are substantially quicker than receiving the internet through copper phone lines.

BT said its programme is the largest single commercial investment ever undertaken in the UK and one of the biggest civil engineering projects currently in operation.

It also announced it is trialling a new type of technology that could help people in remote areas receive broadband for the first time.

It is experimenting with wireless broadband technology on the Isle of Bute in Scotland, in areas of white space where there is a gap in the TV signal.

Liv Garfield, chief executive for BT Openreach, said: "The final 10% of the UK is going to be the hardest to reach with fixed line superfast broadband and so we are busy trialling other technologies.

"It's early days but our hope is that this technology may provide an effective solution for 'not spots' and 'slow spots'."

The company is also to apply for new grants from the Government to help it roll-out more fibre-optic cables in rural areas.

The Government recently said it would make £50 million available to stimulate investment in rural broadband networks in Wiltshire, Norfolk, Devon and Somerset.