David Cameron has called for an "urgent" increase in private investment to improve England's road network.

He said tolls for new roads were one option, alongside attracting more money from pension funds and other investors.

Work was also needed to relieve gridlock by widening "pinch points" and allowing traffic to use motorway hard shoulders, the prime minister said.

But Labour said it would be "wrong" to "load extra costs on ordinary families" to pay for improvements to roads.

In a speech on infrastructure, the prime minister said there was an urgent need to repair its "decades-long degradation" and to "build for the future with as much confidence and ambition as the Victorians once did".

'Sweating old assets'

He argued it was clear there was not enough capacity on the roads in busy areas.

"There's nothing green about a traffic jam - and gridlock holds the economy back," he said.

Part of the solution was to move more people and goods onto the rail network, Mr Cameron said, "but also to widen pinch points, add lanes to motorways by using the hard shoulder to increase capacity and dual overcrowded A-roads".

But the prime minister said "innovative approaches" were needed to finance road improvements at a time of tight government finances.

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"Road tolling is one option - but we are only considering this for new, not existing, capacity. For example, we're looking at how improvements to the A14 could be part-funded through tolling.

"But we now need to be more ambitious. Why is it that other infrastructure - for example water - is funded by private sector capital through privately owned, independently regulated, utilities... but roads in Britain call on the public finances for funding?

"We need to look urgently at the options for getting large-scale private investment into the national roads network, from sovereign wealth funds, pension funds, and other investors."

Mr Cameron also said: "To put it crudely, we've become good in Britain at sweating old assets. But if you do that for too long, there's a price to pay."

He promised to move "from a tactical, piecemeal 'make-do-and-mend' mindset to a strategic, comprehensive, systematic vision".

'Dead-end policy'

Mr Cameron claimed that congestion on roads costs the UK economy £7bn a year.

A feasibility study looking at "new ownership and financing models" for roads will be carried out by the Treasury and Department of Transport, to report by the autumn.

Alasdair Reisner, from the Civil Engineering Contractors' Association, told BBC Radio 4's Today programme that one option was a system of "shadow tolls", whereby the motorist does not pay the cost but private firms are paid by the government depending on the amount of traffic using a road.

Labour leader Ed Miliband said: "We will look at the detail of any scheme but I give the prime minister this warning: people are really hard-pressed; people are struggling to make ends meet.

"I think loading extra costs on ordinary families for using our roads would be the wrong thing to do at this time. It would be wrong for them; it would be wrong for the economy.

"If they want to get the economy moving they should be investing in our infrastructure in order to actually help us build up to the future and get economic growth going."

John Cridland, director-general of the CBI employers' group, said: "Congestion on our roads costs the UK economy up to £8bn a year, so the prime minister's ambition to get much-needed private investment into the strategic network could not have come at a better time."

Edmund King, president of the AA, agreed that investment was needed in roads, but added: "We need to be careful about how we go about this."

On the prime minister's comparison between the water industry and the road network, he said: "Many consumers - drivers - will raise their eyebrows at that. In the water industry we saw big companies make big profits initially, at the same time as water and sewage costs went up by 42% and 36%."

Stephen Glaister, director of the RAC Foundation, said: "We should cautiously welcome the prospect of private sector involvement. There are just not enough public resources to provide the capacity we need and this offers the chance to make long-term plans for a utility every bit as important as things like water, power, electricity and the railways."

But Friends of the Earth's head of campaigns Andrew Pendleton said: "Building and widening roads to tackle congestion is a dead-end policy that will simply lead to more traffic, more pollution - and even more gridlocked roads.

"The prime minister should be promoting alternatives to driving such as affordable buses and trains - and reduce our transport system's reliance on expensive overseas oil."