CRITICS of congestion charging in Edinburgh accused city leaders of ignoring their own consultation process after they began advertising yesterday for companies to operate tolls.

An advertisement appeared in the official Journal of the European Community yesterday - a year before any referendum could take place - inviting bids to operate computer networks and traffic monitoring systems.

Capita, the company behind London's road tolls, confirmed that it would respond to the invitation to tender.

However, Edinburgh council is committed to holding a referendum on tolls, prompting accusations that residents will be railroaded into accepting the plans. A three-month consultation period is due to finish in January.

Kenny MacAskill, the SNP's transport spokesman, said: ''At best it is presumptuous, and at worst it's a flagrant abuse of democracy.''

He added: ''There can be no assumption that the referendum will support it, so it is not only arrogant but is also potentially a waste of public funds.''

The council estimates that tolls - applied at two cordons - would raise (pounds) 900m over 20 years to help pay for improvements to roads and public transport.

Michael Howell, chief executive of Transport Initiatives Edinburgh, the council's arm's-length transport delivery company, said that the advertisement was designed merely to gauge interest.

He added: ''This approach, which had been adopted on a number of major transport and infrastructure projects, ensures upfront costs are minimised and a robust system can be in place from day one if the scheme were to go ahead.''