Mr Watts' announcement will mean that the M25 between junction 12 (M3) and junction 15 (M4) will become Britain's widest road. The scheme does not require planning permission because it is being carried out within the boundaries of the existing road. The Labour party has said it will review the plans should it win the election.
In April 1995, Brian Mawhinney, the then Secretary of State for Transport, announced that he was shelving a scheme to widen this part of the M25 to 14 lanes but announced that the department was examining the 10 and 12 lane scheme as a possible substitute.
Chris Fisher, chairman of the local campaign against the proposal, said: "It is outrageous that ministers continue to reject pleas for a public inquiry into the scheme for the widest motorway in Europe and to ignore 4,000 objections lodged against it." Mr Fisher claimed that the motorway would be full by 2010.
Mr Watts' announcement was made after news emerged that for the first time, the Department of Transport had admitted that the plan to build Terminal Five, in the middle of Britain's longest planning inquiry, was dependent on widening the M25.
Thomas Dockerty, a Highways Agency official giving evidence to the Terminal Five inquiry last month, said the construction of the new terminal was dependent on widening the M25, which will be 12 lanes at the new entrance to the airport.
However, Mr Watts, in a Parliamentary answer last week, said that no such evidence had been given.
The decision also led to a row over parliamentary procedure. Ministerial decisions are not supposed to be made once a general election has been called, even if Parliament is still sitting.
Andrew Mackinlay, Labour MP for Thurrock, attempted to raised the matter with the Cabinet Secretary, who referred him to Sir Patrick Brown, permanent secretary at the Depart-ment of Transport. Sir Patrick said the decision was taken on 13 March, four days before the election announcement.