Foreign-registered and UK lorries will be subject to the same toll

Hauliers would be taxed 15p per kilometre travelled on UK roads, raising an extra �139m annually.

But Professor Alan McKinnon, of Heriot Watt University, said the scheme could cost more than �700 million to run.

He said it would also involve complex technology to track trucks and administration to collect tolls.

The lorry road user charge was announced in the 2002 Budget to ensure truck operators from overseas "pay their fair share" towards UK roads.

Government ministers said it was not expected to be introduced until 2006.

Even at the outset...the proposed system will be highly complex Prof Alan McKinnon Heriot Watt University

The running cost would include administering an "elaborate and costly" rebate scheme to UK lorries, said Prof McKinnon, from the university's logistics research centre.

All 430,000 lorries registered in the UK with gross weights over 3.5 tonnes will be subject to the same charges as foreign lorries, but no revenue will be gained from them as off-setting tax cuts in the form of fuel rebates are due to be introduced.

Customs and Excise said the scheme would be monitored to ensure "value of money".

"We have only just begun the procurement process for potential suppliers so it is somewhat premature for this academic speculation about the out-turn costs of the scheme," a spokeswoman said.

She emphasised that UK hauliers will receive fuel duty rebates.

"We expect the eventual costs to be in line with the business case for the scheme."

'Challenges'

The fuel duty rebates could amount to �3bn, presenting the need for two "revenue streams" to be created to deal with incoming tolls and outgoing fuel rebates, Prof McKinnon said.

Vehicle tracking and toll collection will also present technological and organisational "challenges", he added.

"If the creation of a 'level playing field' for British and foreign hauliers is the main justification for the [charge], we are taking a sledgehammer to crack a nut."

He highlighted the integration of all the technology, including satellite tracking and microwave systems, as well as the registering of vehicles, operators and authorised fitters of tracking equipment as potential challenges.

Delay recommended

"Even at the outset...the proposed system will be highly complex."

He concluded in his 17-page report that the scheme "cannot be justified solely as a means of levelling the playing field with foreign operators.

"There is a growing view among British road hauliers that, under the pretext of taxing foreign trucks, the government is about to saddle them with a complex tolling system that will be expensive to implement and create a major new revenue stream for the Exchequer."

He recommended that the introduction of the charge be delayed until road-user charging is applied to all categories of road traffic, not just lorries.

He also said it should be delayed until GPS-based tracking is improved across the EU and common standards of electronic road tolling had been established in the EU.