The committee is putting forward options to get freight moving

A report by Holyrood's transport committee also said grants to encourage firms to transport freight by rail, water and air should continue.

The road network currently handles 70% of all freight tonnage.

Other proposals in the report included higher lorry speed limits on some single carriageway roads, such as the A9, and relaxing night deliveries.

The Scottish Executive previously voted to retain the freight facilities grant, which aims to attract traffic to rail or waterways, after it was suspended in England.

We are concerned that the executive may not adequately assess the environmental and social benefits that arise from these grants Bristow Muldoon Transport committee chairman

Transport committee chairman Bristow Muldoon said, while it was disappointing a greater shift of freight from the roads had not taken place, it backed the grant as an effective means of encouraging a "modal shift".

He added: "Nevertheless, we are concerned that the executive may not adequately assess the environmental and social benefits that arise from these grants.

"It could be timely to assess how cost-effective this scheme remains in securing environmental benefits in the transport sector."

Speed review

Other reforms suggested included a dedicated port policy, allowing companies to run trucks on forest roads using red diesel - special reduced tax fuel - and the promotion of better roadside facilities for lorries.

The A9 between Perth and Inverness was put forward as one road where lorry speed limits could be increased from 40mph to 50mph.

The Road Haulage Association (RHA) welcomed the report but said its main concerns would have to be addressed by Westminster.

Many freight companies are finding it impossible to compete against foreign lorries Fergus Ewing SNP transport spokesman

Phil Flanders, RHA director for Scotland and Northern Ireland, said: "Scottish hauliers pay more for their fuel than anywhere in the UK.

"They also have longer distances to travel to the main markets, which impinges on working time and drivers' hours' regulations."

Mr Flanders said the committee's proposals would make a difference but predicted HM Revenue & Customs would strongly oppose the red diesel plan.

The committee inquiry, which was launched last October, followed a petition by the RHA on behalf of the industry.

Scottish National Party transport spokesman Fergus Ewing said: "Scotland's freight transport industry should be recognised as a vital part of our economy.

"Many freight companies are finding it impossible to compete against foreign lorries, because the diesel duty imposed by Gordon Brown is the highest in the EU.