Microsoft yesterday launched a stinging attack on BT, accusing the former state-owned monoply of spoiling the rapid roll out of high speed web connections.

Neil Holloway, Microsoft's UK managing director, claimed it was in BT's interest to delay rivals from launching super-fast ADSL net services.

"It does seem ironic that one minute the government is saying the local loop is going to be opened up in June or July next year and ... the next we hear there's not enough room [in BT's exchanges], it's the wrong type of carpet, the air conditioning was wrong on a Wednesday afternoon," he said.

"It's not in BT's interest to get everyone else to roll it out. The longer they can delay it, the better."

Earlier this month US telco WorldCom pulled out of the broadband market - after reports that it was "frustrated" with Oftel's handling of the process opening up BT's monopoly to competition.

Another player in the high speed web market, RSL Communications, pulled out of the first stage of bidding and accused the industry's regulator of failing to ensure fair play for rivals to BT.

The company was also under fire yesterday after it was revealed that that nearly 40% of the British population - around 23m people - will be excluded from the high speed internet revolution.

Leaked BT documents suggested that the company predicts there will be "dead zones" where the new services will be "commercially and technically unviable".

Those most likely to miss out were said to be businesses and consumers in Cornwall, Wales, the North East and North West, Scotland and Northern Ireland.

But a spokeswoman for BT dismissed the claims and emphasised there was nothing secret or underhand about the roll-out programme.

The company, she said, had always maintained the initial roll-out would only cover around 75% of the population as there were technical and geographical barriers.

"We have always said that beyond next spring it will depend on what demand there is for these new services," she said. "If there was huge provider demand we could invest more in our local network to take it further out.

"If there is demand, we're not going to sit there and not go for it."

The spokeswoman also refuted claims that BT was dragging its feet with the roll-out.

"We are working to a timetable laid down by the entire telecoms industry in the UK," she said.

"That is designed to open up BT's exchange to allow even more competition for broadband internet."

Mr Holloway also noted that a link-up between Telewest and NTL - in which Microsoft own stakes of 23.7% and 3% respectively - would "speed up competition between cable, ADSL, satellite and wireless".

Neither NTL nor Telewest were prepared to comment last night.

However, industry sources said the pair were already working closely with each other and suggestions of a merger were being made.

A deal would have to attract the support of France Telecom, which owns 23% of NTL and UPC NV, the Dutch cable operator, which has a 25% stakeholding in Telewest.

This week's debate over broadband services will be another blow for Tony Blair's plan to get Britain online.

It follows in the wake of the farce earlier this year over unmetered internet access after payment of a flat fee.

AltaVista, the American internet portal and software producer, was encouraged to take a leading role but had to withdraw its service as it proved to economically unviable.

Last week America Online stoked up the war between internet service providers by offering unlimited use of the web and free customer support for £15 a month.