The number of 'sub-standard' bridges in the UK has soared in recent years and would cost almost £1 billion to repair, according to alarming new findings.

A survey by the RAC Foundation revealed that almost 3,500 British bridges maintained by councils are not considered strong enough to bear 44-ton lorries – the heaviest vehicles permitted on our roads – placing them at risk of collapse if warning signs are ignored.

The figure – an increase of almost 45 per cent from the 2,375 recorded in 2015 – was correlated after the motoring research charity sent out Freedom of Information requests to all local authorities.

Eastham Bridge was reduced to rubble after it dramatically crumbled into the River Teme in Tenbury Wells, Worcester in 2015

Experts at the RAC Foundation believe that reduced maintenance due to budget constraints is partly to blame for the substantial increase, while calculating that the one-off cost of bringing all 'substandard' bridges up to scratch would be around £934 million, or £271,000 per structure.

The current total of 3,441 bridges regarded as 'sub-standard' – using the widely used 44-ton measure – represents 4.6 per cent of the 74,000 bridges on the UK's local road network, or around one in 22 of the total.

And while a repeat of a Genoa-like disaster is considered extremely unlikely, bridge collapses on a far smaller scale are not unknown in the UK.

In 2016, a school bus carrying 11 pupils nearly plunged into the River Teme when the 225-year-old Eastham Bridge suddenly collapsed in Tenbury Wells, Worcestershire.

The driver noticed the road crumbling away and safely reversed off the Grade II-listed structure as it fell apart.

This bridge over the River Wharfe that collapsed due to flooding on December 30, 2015 in Tadcaster, England, after Storm Frank

An investigation concluded that the bridge had collapsed after fast-flowing water eroded the base of one of its piers.

Councils said that many bridges in the 'sub-standard' category were older structures that were often built on country lanes and never designed for heavy traffic.

But the RAC Foundation believes an increasing number of bridges that had previously been able to support heavy lorries are now unable to.

It also claims that many such structures now have weight restrictions for the first time, while others are 'under programmes of increased monitoring or even managed decline'.

There have been many cases in recent years of heavy vehicles courting disaster by crossing bridges with weight restrictions.

The three-ton weight limit on the historic 200-year-old bridge across the Thames in Marlow, Buckinghamshire, is frequently flouted by HGV drivers.

One, who ended up on the bridge while following his satellite navigation system, caused £200,000 of damage when he got stuck on it in September 2016.

Lorry drivers have also been repeatedly fined for breaking the 7.5-ton restriction on England's longest stone bridge at Swarkestone, Derbyshire, which dates back 700 years.

The RAC Foundation collected data for its survey from 204 of the 207 highways authorities in England, Scotland and Wales, which replied to its Freedom of Information requests.

Suspension bridge in Marlow, Buckinghamshire, which was opened in 1832, has been closed due to damage when a HGV lorry tried to cross it

It found that if money was no object, then councils would 'ideally' want to bring 2,077 of the 'sub-standard' bridges back up to standard.

But budget restrictions meant that councils anticipated only 370 of the bridges would have the necessary work carried out on them within the next five years.

Steve Gooding, director of the RAC Foundation, said: 'The road maintenance crisis faced by financially beleaguered councils is often reported in terms of potholes to be filled.

'This research hints at the wide spectrum of things needing attention, including blocked gulleys, overgrown verges and, of course, fragile bridges.'