Royal Mail chairman Allan Leighton said he was "shocked" by the charge and warned that legal action might be launched to challenge the proposals.

The regulator Postcomm decided last year that rival companies should be able to collect their own customers' mail and take it to sorting offices for the Royal Mail to make the final delivery to people's homes.

Now Postcomm has announced the proposed scale of charges for the first new entrant, UK Mail, which is owned by Business Post.

'A spanner in the works'

Under the new access arrangement, UK Mail will collect mail from customers, take it to its Birmingham centre, then send it to the Royal Mail's 1,400 delivery offices where postmen and postwomen will deliver it to its final destination.

I'm confident we can get back to profitability - but not unless Postcomm's plans give Royal Mail a realistic commercial price for access Allan Leighton, Royal Mail chairman

Postcomm is proposing charges ranging from 11.46p to �4.06, depending on the weight of the mail.

The 11.46p charge for an ordinary letter compares with current stamp prices of 28p for first class delivery and 20p for second class.

Allan Leighton said the proposals could "throw a spanner in the works" of the attempts to repair the Royal Mail's finances.

The organisation is currently shedding thousands of jobs and restructuring the firm in order to stem its huge losses.

"Royal Mail will shortly be announcing its results for the last financial year and they'll show we've cut significantly our losses and started to turn the company around," Mr Leighton said.

"I'm confident we can get back to profitability - but not unless Postcomm's plans give Royal Mail a realistic commercial price for access."

Legal threat

Mr Leighton said the Royal Mail would be scrutinising Postcomm's proposals.

UK Mail has been asked to pay rather more than we had hoped Paul Carvell, Business Post chief executive

"If the regulator has got the access arrangements wrong then it means the destruction of the universal one-price-goes-anywhere service.

"It will mean a two-tier or even a multi-tier postal service where the price of sending a letter depends on the distance it is travelling."

And he added that legal action could be a possibility if the Royal Mail thought Postcomm had got its sums wrong.

"If Postcomm's plans amount to a green light for rival firms to creamskim profitable mail and leave Royal Mail without the means to provide the universal service, then we will not hesitate to fight the regulator's plans in the High Court and, if necessary, the European Court."

'Effective competition'

Postcomm chairman Graham Corbett defended the move.

"This is a crucially important step in opening up the postal market in a way which supports the universal service.

"We are aware that Royal Mail is sensitive to loss of volumes but if the price is pitched too high that would not only deter the development of effective competition but in due course companies could set up alternative delivery networks leading to a much riskier market for Royal Mail and everyone else."

Postcomm said it did not expect the access proposals "to have any significant effect on Royal Mail's ability to provide the universal service".

Business Post chief executive Paul Carvell said: "UK Mail has been asked to pay rather more than we had hoped.

"However, after 18 months since UK Mail was granted its interim licence, we are keen to get on with the launch of our new service which has stimulated a lot of interest among many large business customers."

Interested parties have three months to comment on Postcomm's proposals, with a 20 August deadline for replies.