It will take around 15 years to clear the backlog of road maintenance in London, a new survey has revealed.

That's what the Annual Local Authority Road Maintenance (ALARM) survey found.

It also found that, despite the alarming news, there has been a big increase in the number of potholes repaired across the capital.

Of all roads in London, 17% were in a poor structural condition in 2014/15, down 19% from the year before.

Each year the Asphalt Industry Alliance (AIA) commissions an independent survey of all local authority highways departments in England and Wales.

In 2014/15, councils in London filled 4,993 potholes, up by 39% from 3,602 in 2013/14. The average cost to fill a pothole is £72, with councils spending a total of £11.5m in 2014/15.

The research also found that poor road conditions have led to an average of 127 compensation claims per council in 2014/15 with councils in London each paying an average of £66,216.

Across London, 28% of councils reported unforeseen road maintenance costs, averaging an extra £810,000 per council.

In the survey, highways departments were asked to estimate just how much it would cost to bring their road networks up to scratch. The responses to the survey have led to an estimation that councils in London would need £807m, or an average of £25.2m each, to clear the backlog.

Alan Mackenzie, AIA chairman, said: "It is 20 years since the Annual Local Authority Road Maintenance (ALARM) survey was introduced to provide a detailed picture of the condition of the local road network.

"During that time we have seen five governments and 10 different Secretaries of State for Transport but, when it comes to our roads, little has changed; much of the network is still crumbling and a huge backlog of repairs still need to be tackled.

"It's true that the level of shortfall between what highways engineers need to maintain their roads properly and what they actually receive has decreased substantially over the last two decades. This is a testament to successive governments' acknowledgement of the importance of the issue.

"The first ALARM survey, published in 1996, showed an average shortfall of £9m per authority, while this year's figure is just over £3.2m.

"While we are moving in the right direction, the results of this year's survey again highlight the scale of the task that remains. One in six of our roads is classed as being in poor condition and local authorities still need over £12bn, the same amount reported last year, to bring the network up to scratch."