Internet service providers have asked the government to intervene over the price being set to give them access to BT's physical infrastructure.
Giving rivals access to BT ducts and poles is seen as a crucial element to get fast broadband to rural areas.
But ISPs argue that the prices set by BT are four to five times higher than their underlying costs.
BT said that its prices were reasonable and laid down the gauntlet to rivals.
"The fact is our proposed prices for duct access compare very well with European averages," the telco said in a statement.
"BT is the only company who has installed broadband equipment in exchanges serving the last 10% of the UK and so we would question whether these companies are genuinely interested in serving rural Britain given their track record.
"It is highly ironic that we are being criticised by some companies who provide little or no wholesale access to their assets," it added.
BT set the price for duct sharing in January. Prices vary but start at £0.95 per metre, per annum.
For the sharing of overhead poles, Openreach proposed a price of £21 per pole attachment.
But ISPs believe the prices are far too high.
In a joint letter to communications minister Ed Vaizey, ISPs warn that plans to open up BT's ducts will not work if the price isn't cut.
The letter, signed by Virgin Media and TalkTalk among others says the Physical Infrastructure Access (PIA) trial, which is one of the current government's key broadband policies, "will be a commercial and policy failure if Openreach does not revise its prices".
Openreach is the BT spin-off responsible for maintaining the telco's network.
In the letter Virgin Media said: "It would be more cost effective to build an entirely separate duct and pole network in parallel with BT's existing network".
So far one one company has signed up to the duct-sharing scheme.
BT said that it was "disappointing that this letter was shared with the media several hours before ourselves".
"It's a shame that some of the companies involved seem keener to spend more time talking about this process than actually working on it.
The news comes as BT cranks up the speed on its copper network, to deliver up to 20Mbps (megabits per second) to 80% of UK homes by the end of the year.
Few households are likely to get top speeds because of the limitations of the ADSL technology.
Ofcom estimates that the average speed for an "up to 20Mbps" package is 6.2Mbps.
The telco has also revealed that its Fibre-to-the-Cabinet (FTTC) technology now reaches four million homes.
Some 30 ISPs are offering customers FTTC, buying it wholesale from BT.
It offers speeds of up to 40Mbps and is now available to more than 4 million homes and businesses.
By 2015, BT has pledged to offer some form of fibre broadband to two-thirds of homes in the UK.
To ensure the final third does not miss out, the government has set aside a £530m fund, drawn from the BBC licence fee that was originally earmarked to help the transition to digital switchover.
Four pilots areas intended as testbeds for rural broadband are due to be allocated at the end of April.
The government has also invited councils to bid for some of the money.