Tony Blair is to send an e-mail to the million-plus people behind an online petition against road pricing telling them it is "surely part of the answer".
Downing St set up online petitions in November 2006
Mr Blair told the Observer he did not expect to win critics over at once, but a useful debate had been started.
The petition calls the policy "sinister and wrong" and warns the charge would be unfair to those who live away from their families, and poorer people
The petition was so popular that at one point it crashed the PM's website.
It appears on a new section of Downing Street's website which was set up in November last year to allow anyone to address and deliver a petition directly to the Prime Minister.
Transport Secretary Douglas Alexander has accused the organisers of the petition on the 10 Downing Street website of spreading "myths" and pledged to press ahead with plans to pilot the scheme.
The man who started the petition, account manager Peter Roberts, 46, from Telford, has confessed to being "staggered" by the response and called for a meeting with government officials.
Mr Blair told the Observer he welcomed the petition "not because I share the petitioners' views - I don't - but because I know the country needs to have a full debate on how we tackle road congestion and this petition has helped spark it."
"Over the next few days I will be sending out a response to everyone who has signed the petition against road charging explaining the problems the country faces and why I believe road pricing is surely part of the answer here as it is in many other countries.
"I'm not kidding myself that this will change people's views overnight.
"I am convinced, however, that the focus on this issue that the e-petition has brought about will help improve our understanding of the problems and the realisation that there are no cost-free answers.
"And that surely has got to be good news for the health of our democracy and for the chances of our country coming up with the right and sustainable solutions to the long-term challenges we face," he said.
The PM noted that, after being criticised in the past as a "control freak", he was now "under attack for allowing dissenting views on my own website".
The Observer reported that the government was considering introducing road pricing on a voluntary basis initially.
Under plans suggested by the RAC Foundation, drivers who choose to have satellite-tracking equipment to measure how far and where they travel could be given discounts on other motoring taxes.
One scheme is for people to pay their tolls at the fuel pump in return for discounts on petrol duty.