Controversial proposals to introduce road tolls in Edinburgh have been approved in principle by councillors.

The local authority will now submit the plans to Transport Minister Iain Gray.

If the Scottish Executive sanctions the project a referendum will be held in the city on the detailed plans.

There's absolutely no prospect of any use of the charging scheme until June or July 2006 at the earliest

Cllr Andrew Burns

However, councillors heard on Thursday that such a move could be years away.

Transport chief Andrew Burns said: "All we did today was pass an application that includes the promise of a referendum before any final implementation of a road congestion scheme.

"It's a very early hurdle and there's absolutely no prospect of any use of the charging scheme until June or July 2006 at the earliest."

The plans were approved in principle despite criticism from opposition Conservative and Liberal Democrat councillors.

Tory group leader Iain White said his party had voted against the proposals because it was opposed to charging on principle.

Council elections

"The fact that they are going ahead with the referendum is a bit unhelpful because they won't tell us when it will be or what the question will be," he said.

"People have a chance to say no to tolls at next year's council elections, come what may."

Cllr Burns stressed that the referendum would not take place until the proposals have been finalised.

Drivers would be charged to enter the city centre

Under the draft scheme, a two-cordon toll would be set up charging motorists �2 to enter Edinburgh.

The first cordon at the city bypass would only be operational during the morning and evening peak periods.

A second cordon would surround the city centre from 0700 till 1830 BST on week days.

Householders in the capital have already been given the chance to take part in a consultation process into the proposals.

However, that exercise failed to produce a clear result.

Package of changes

Planners have said that, if unchecked, traffic levels across the city would grow by 20% in the next 20 years and congestion would almost double.

It has been estimated that the tolls would raise �70m a year.

That money would fund a package of changes including the reintroduction of trams and improved bus and train services.