A government decision announced last week to raise the speed limit for lorries on single carriageway rural roads from 40 miles an hour to 50 miles an hour has been criticised by the opposition and by cycling organisations – and even the Government’s own impact assessment suggests casualties could rise by between 10 and 20 per cent.

Announcing the change in the speed limit, which is due to come into force next year, transport minister Claire Perry insisted that the higher speed limit would “cut dangerous overtaking by motorists seeking to pass slower-moving lorries in front of them", reports The Guardian.

But an impact assessment carried out by the Department for Transport (DfT) says that the higher speed limit for HGVs would lead to two or three additional fatal road traffic incidents a year and between four and nine serious ones.

Turning to whether the change would reduce the amount of dangerous overtaking, the authors said it could be a benefit but they were unable to put a figure on it "because we do not have sufficient confidence that it would occur," adding, "while overtaking manoeuvres may become less likely, they would also be performed at higher speeds and so could become more dangerous".

The assessment added that three quarters of lorry drivers are thought to break the speed limit regularly when driving on roads without speed cameras.

The DfT insisted it had examined the issue in detail before deciding to increase the speed limit, with a spokesman saying: "Road safety is a key priority and we studied both the potential for increased risk and for improved safety due to less risky overtaking before making our decision.

“We are determined to improve safety – for instance, by encouraging local authorities to lower speed limits on roads where needed, better procedures to deal with HGV drivers who drive tired, and bringing in a new offence of causing serious injury by dangerous driving."

But shadow transport secretary Mary Creagh accused the government of putting the lives of vulnerable road users at risk.

She said: "The government has pledged to review the safety of rural roads, but these higher speed limits will make them much less safe for pedestrians and cyclists. Ministers need to bring forward evidence before pushing ahead with these potentially dangerous speed increases."

Responding to a government claim that the new speed limit would save the haulage sector some £11 million a year, she added: "The main impact on the freight industry is that the government has failed to tackle the strategic road network, cancelling projects to improve roads and cutting building and maintenance budgets."

British Cycling described the move as “staggering,” while Penny Knight, head of the cycling team at the law firm Leigh Day, criticised the government for putting financial interests over people’s safety.

“It is extraordinary that the cost savings to the haulage industry are being cited as the reasons for making our roads more unsafe for all road users, not just cyclists,” she said. “Any cost savings to an industry are not worth the deaths that will result from this legislation."

Referring to the Commonwealth Games, she added: “The timing of this announcement couldn’t be worse, just when we celebrate cycling as one of our key sporting events as a nation, the Government ensures that the roads on which many of our champions train are made more unsafe."

Chris Peck, policy co-ordinator at national cyclist’s organisation CTC, pointed out that the roads where lorries will soon be permitted to travel faster than they can at the moment are the very ones that already account for a high proportion of cycling casualties.

He said: "The risk of cycling on rural single-carriageway roads is over 20 times greater than on minor urban roads, and several cyclists are killed each year – hit behind by lorries on these roads – a risk which will only increase as lorries are allowed to go faster.

“CTC believes that lorries should only be allowed to drive at higher speeds on properly engineered major roads, where adequate parallel cycling facilities exist," he added.

It also seems likely that increasing the HGV speed limits on these roads will increase the number of lorries using them, a factor that does not seem to have been accounted for in the DfT's calculations.

Drivers using GPS navigation will be more likely to be directed down single-carriageway roads by algorithms designed to shorten journey time if those roads become nominally faster.

News of the change to the speed limit was however welcomed by the Road Haulage Association (RHA) which said: "This evidence-based decision by ministers will be strongly welcomed by hauliers and their drivers. The current limit is long out-of-date and the frustration it generates causes unnecessary road safety risks."