Cyclists have complained that new security barriers on London’s bridges make roads less safe for them, just hours after they were installed to protect pedestrians from terror attacks.

Campaigners said the reinforced fences, which have been set up in cycle lanes to shield crowds walking on bridges, were a “crush risk” and showed a “total lack of consideration” for the welfare of cyclists.

The sturdy partitions were put in place overnight on crossings at Waterloo, Lambeth and Westminster in response to the deadly terror strike in the heart of the capital on Saturday evening.

In the attack, three men drove a white van on to the pavement and mowed down pedestrians on London Bridge before going on a knife rampage through Borough Market, leaving seven dead and dozens injured.

Hours after the safety barriers appeared, cyclists expressed concerns about the effect they would have on vulnerable road users on major routes through central London that are popular with riders.

Transport blogger and cyclist Mark Treasure said the fences left “anyone cycling totally unprotected” and suggested they should be between the cycle lane and the road instead.

He added: “I suppose I shouldn’t be surprised by the total lack of consideration for the safety of any human being cycling here, but hey ho.”

Guardian journalist Peter Walker, author Bike Nation: How Cycling Can Save the World, tweeted: “The high concrete barriers on Westminster (and one side of Lambeth) bridge make sense for security, but could be perilous for cyclists.”

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He went on: “Again, not to necessarily say barriers should never be used, but I fear these haven't been thought out 100% for safety.”

John Burke added: "Those barriers present a crush risk if a cyclist is forced left by a motor vehicle."

Transport groups also expressed doubts about the scheme.

A spokesman for the London Cycling Campaign said: “London Cycling Campaign is fully supportive of the Met, TfL and the boroughs involved taking urgent steps to provide extra protection for Londoners and visitors to our city.

“It is also important that we do not allow this attack to impede people going about their business, including being able to cycle safely around the city.”

Matt Winfield, London deputy director at walking and cycling charity Sustrans, said: "Being able to walk and cycle safely is crucial to London’s vitality. A small change to the barriers so that they protect people on bikes as well as pedestrians would ensure the roads are safer for cycling too."

Twitter user Northern Cyclist TVL suggested a solution, posting: "Why not place the barriers to the right of the cycle lane and protect cyclists at the same time. Didn't they think about the vulnerable?"

Transport safety campaigner Tom Kearney, who was put in a coma after being hit by bus in 2009, said: "#FacePalm Khan wastes opportunity to create a PopUp #Protected Cycleway & Footway."

And a cyclist who uses the Twitter username #TrafficDroid wrote: "regarding the barrier on the bridge... should have been increased further to protect cyclists as well as pedestrians. missed opportunity."

The barriers have been erected following two similar attacks on London in recent months where Islamist terrorists used vehicles to kill pedestrians on bridges.

Many have welcomed the measures but police, TfL and council officials have been left facing serious questions over why they were not installed immediately after March's attack on Westminster.

Khalid Masood killed four pedestrians and injured about 50 others on March 22 as he ploughed into people in a grey Hyundai while they walked on Westminster Bridge.

Westminster Council today failed to answer questions why the fences, erected overnight in a matter of hours, had not been put in place earlier.

A spokesman for Westminster Council told the Standard: “The timing issue is one for Met police not us – they determine when these kinds of measures are put into [place], not us.”

But a spokeswoman for the Met Police said it would not comment on the measures.

The barriers are thought to be temporary, but Westminster Council leader Nickie Aiken said she believed they should remain indefinitely.

"People in Westminster need this kind of protective measure – it is sensible and proportionate," she said.

"We are working closely with the Metropolitan police and security services and are happy to assist on measures like planning and traffic management.

"The kind of security barrier now in place on Westminster Bridge needs to be part of a permanent solution."