Motorists are being "fleeced" by government taxation, with drivers paying £42 billion a year to the Treasury, a campaign group has said.

Yet only 18.6% of this road-user tax goes back into roads infrastructure, according to research commissioned by FairFuelUK.

The research, from polling company ComRes, showed 26.8% of the amount raised by road taxes went on public transport, with 54.6% supporting other Government spending.

Also, 69% of the 2,024 people surveyed by ComRes said they thought FairFuelUK's call for a 3p-a-litre fuel duty cut would benefit the economy.

The figures are being released today as FairFuelUK, whose backers include the RAC and the Freight Transport Association, launches its general election manifesto at Westminster.

FairFuelUK campaign founder Howard Cox said: "Time is up for the Treasury to stop fleecing 70% of the electorate from punitively taxing an essential, no-choice-but-to-use resource.

"Instead of taking more than 60% every time we fill up at the pumps, they should be motivating the economy by cutting this taxation."

MP Jason McCartney (Con, Colne Valley) said: "The research clearly demonstrates that fuel duty and the cost of running a car is still a great concern for families across the UK.

"Cutting fuel duty would benefit the UK economy as a whole as well as relieving the financial burden on households that run a car."

In separate research, the RAC Foundation said that in 2012 a total of £30.7 billion was raised from direct motoring taxation (excluding VAT).

The foundation added that in the same year just £7.5 billion (24% of motoring tax income) was spent on the road network: £3 billion of it on national roads and £4.5 billion on local roads.

The research, f rom transport consultant David Bayliss, showed that the Treasury now receives, in broad terms, a net 9p per mile travelled by car and van drivers.

RAC Foundation director Professor Stephen Glaister said: "Over the past five years the gap between the Chancellor's income from motoring tax and what he spends on roads has widened sharply.

"At the same time the pothole backlog has been growing and local authorities are warning that spending commitments on social care and environmental services means there will be even less money available to maintain our highways in the future."

AA president Edmund King said: "Despite a drop in pump prices, our AA/Populus surveys still show that drivers are feeling the pinch.

"A majority of drivers (57%) disagree that they are more relaxed about pump prices and have not started to use their cars more. These findings from our poll of 18,000 drivers are reflected in the fuel sale figures, which also show a drop.

"We have also found that a majority of drivers have adopted fuel-saving habits such as combining road trips, driving more moderately and walking/cycling short journeys and intend to stick with them despite lower pump prices.

"Drivers still don't feel that they are getting value for money when they navigate pot-holed and congested roads."

A Government spokesman said: "This Government has frozen fuel duty, meaning that petrol will be nearly 20p a litre cheaper by the end of the parliament than it otherwise would have been, and a typical motorist will save £680 in total by 2015-16.

"At Budget 2014 we announced the £200 million Pothole Fund for local authorities, to fix a potential 3.2 million potholes across England.

"This is the latest in a series of announcements which will see more than £24 billion spent on England's strategic road network between 2010 and 2021 - the biggest upgrade to our roads in over 30 years and a crucial part of the Government's long-term economic plan."