The M6 Toll is set to become one of the most expensive in Europe after its eighth price rise in nine years next month.

From March 1 car drivers will be charged £5.50 to use it during the day – a rise of 20p; while trailers, vans and lorries will have to stump up £11 – an extra 40p.

The latest figures show the number of vehicles using the M6 Toll is falling while traffic on the neighbouring M6 is soaring.

Figures from the Highways Agency show about 160,000 vehicles a day use the J5 to J8 stretch of the M6 – more than four times the number which uses the toll road.

The privately-owned 26-mile road, which was opened in 2004 and cost £900 million to build, was aimed at cutting chronic congestion on the M6.

When it was launched, the cost of a car using it was just £2.

The road stretches 27 miles from Junction 11a on the M6 near Cannock, and re-joins the M6 at Junction 3a at Coleshill.

Figures released by the toll road’s operators, Midland Expressway Ltd (MEL), show that during the period October to December 2011 the average traffic flow was 34,286, a drop of 10.7 per cent on the same period in 2010.

But MEL insisted these figures were not a cause for concern.

A spokesman said: “Overall the low traffic volumes were primarily due to continuing weak economic conditions.”

“Increasing a toll is not a decision we take lightly and we believe the new toll levels remain unbeatable value for money.”

A spokeswoman for the Road Haulage Association, which represents lorry drivers and haulage companies, said: “It costs too much and every penny a haulier pays they have to get back.

“It’s almost as if the M6 Toll operators are trying to price people away from using it.”

Michael Ward, president of Birmingham Chamber of Commerce said: “Given how price conscious consumers are at the moment it’s vital the M6 Toll be priced competitively.

“We appreciate the need to make a profit, but we feel that by lowering prices profits would still be maintained due to increased patronage.”

Travelling the length of the M6 Toll will work out at a cost of around 20p or 15 euro cents per mile when the new charges come in in March.

The figure is comparable to charges on what are classed as some of Europe’s most expensive toll roads, though anyone using the M6 Toll to travel just a junction or two would see their per mile charge rocket.

Portugal’s A1 from Lisbon to Porto charges motorists 19.55 euros to travel a distance of 197 miles, meaning the entire journey would work out at less than ten cents per mile.

Spain’s A7 from Tarragona to Valencia charges 22 euros to travel 160 miles, a charge of around 13 cents per mile.

A more expensive option is Austria’s Gross Glockner Alpine Road, which at a cost of 28 euros for just over 29 miles is not far short of a euro per mile – but the views more than compensate drivers for the high cost.

Even cash-strapped Greece’s A1/E75 between Larisa and Lamia (41.6 miles) is cheaper than the M6 Toll with a charge of 12.5 cents per mile.