Tony Blair today defended the Government's plans to charge motorists for every mile they drive by insisting that Britain faces traffic gridlock without action.

The Prime Minister sent a four-page e-mail to 1.79 million people who signed an online Downing Street petition opposing road pricing.

Peter Roberts, 46, from Telford in Shropshire, along with other members of the Association of British Drivers who set up the petition, received their replies just after midnight when the petition closed, with 1,792,168 signatures.

Such is the volume of e-mails required, Downing Street is to send them in batches over the next few days to avoid overloading its computer system.

The Prime Minister's e-mail caused controversy, however, with Conservatives expressing concern that the huge database gleaned from the Downing Street petitions site - which is taxpayer-funded - could be used by Labour for party political purposes.

Chris Grayling, the Tory shadow transport secretary, wrote to Sir Gus O'Donnell, Britain's top civil servant, asking for clarification that this would not be the case.

Downing Street denied the Tory claims, insisting that the e-mail addresses submitted by signatories could only be used twice each under Data Protection rules - and adding that the blogging charity mysociety, which co-runs the petitions, controls the database so it would not fall into Labour Party hands.

In his e-mail to the petition signatories, Mr Blair said: "Congestion is a major problem to which there is no easy answer," adding that it was forecasted to increase by 25 per cent by 2015.

The Prime Minister explained that the independent Eddington Study, which was designed to review Britain's transport network, highlighted "how road pricing could provide a solution to these problems and that advances in technology put these plans within our reach".

Such a system could see motorists who drive the longest distances at peak times paying more to use their cars, he added.

"This could mean that those who use their car less, or can travel at less congested times in less congested areas, for example in rural areas, would benefit from lower motoring costs overall," Mr Blair wrote.

However the Prime Minister sought to reassure petitioners opposed to the scheme by saying that no final decision had been taken, adding that the Government was not "rushing headlong" into the action without considering all options.

"Of course, it would be 10 years or more before any national scheme was technologically, never mind politically, feasible," he said.

The RAC motoring group reacted to the e-mail by saying that the Government had to come clean about the details of such an initiative.

Edmund King, the executive director of the RAC Foundation, said: "There has been a big void. There has been talk about road pricing but we do not really know how it would affect us as individuals.

"We are not surprised at the protests. It shows to us that the way the debate has been going has to change and the Government have to, if you like, ‘lay out their stall’.

"You cannot expect people to support something when they do not know how it will affect them."

He added: "If the Government is serious about this, they have to set up an independent commission to take it forward and get motorists on that commission."

Paul Walters, head of public affairs at the AA, said Governments across Europe had always faced hostile public opinion when trying to introduce road pricing schemes.

"It is a very emotive issue and of course European Governments have always experienced problems like this when they have talked about road pricing," he said.

"I think it is going to take time. People clearly are not convinced at the moment and I do not think, however much assurances are given, that they will feel truly comfortable with this policy."

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