BT Group has kicked off a broadband arms race by offering selected households internet access of up to 110 megabits per second, the fastest on a national network in Britain, and powerful enough to download a feature film in one minute.

In an effort to best Virgin Media, whose top speed is 100Mbps, and to counter critics in industry and government who say the UK's introduction of fibre-optics has been too slow, BT also vowed to offer the same homes speeds of up to 300Mbps by next spring.

However, the service will initially be available at only six exchanges – Milton Keynes, Ashford in Middlesex, York, north London, Chester and St Austell – covering 60,000 homes.

The new speeds have been made possible because in these areas BT is for the first time installing fibre directly to homes, rather than to street cabinets with copper wire carrying the signal from the cabinet to the doorstep.

BT currently reaches 5m homes with fibre to the cabinet, and on Wednesday said these customers would begin to see speeds double from 40Mbps to 80Mbps.

Chief executive Ian Livingston said he hoped 10m of the UK's 25m households would have some form of fibre connection by next year. BT has vowed to get fibre to 18m homes by 2015. "We'll hit the government's target of having the best superfast broadband in Europe by 2015," he said.

About 200,000 customers have so far bought superfast broadband from BT, while Virgin Media has 930,000 customers on speeds of 30Mbps and above.

BT says that, with fibre to the premises, speeds of up to 1 gigabit per second – nearly 10 times faster than the 110Mbps product – will eventually be commercially available. A 1Gbps trial is under way in Kesgrave in Suffolk.

Jeremy Hunt this summer urged BT to pick up the pace on fibre, and a trade association representing telecoms departments at UK businesses has accused BT of stalling tactics, and called for the company to be broken up.

The Communications Management Association (CMA), which represents 30 corporate members in finance, retail and local government, is worried the UK is falling behind other European nations and has called on the UK to follow New Zealand's example and hive off BT's Openreach division, which builds and manages the former telecoms monopoly's network.

"While this would pose new regulatory challenges (and further interminable delaying arguments), the prospects facing business users could hardly be worse than they are now," the CMA said.