Birmingham’s largest bus operator has threatened to suspend a major service because crumbling roads means double deckers are getting stuck on speed humps.

National Express has said it will withdraw the 35 service through Kings Heath if deep potholes and cracks in Allen’s Croft Road are not filled in.

The company claims buses are being damaged on a daily basis, costing thousands of pounds in repairs, and could even put passengers at risk.

National Express said it had reported the problem to the city council and its road repair firm Amey several times, claiming that holes surrounding speed bumps raise them to the extent that they are scraping the undersides of buses.

Amey, which in June began a £2.7 billion contract to repair and maintain Birmingham’s roads for 25 years, has so far done nothing.

National Express has already spent thousands repairing gearboxes and suspension and fears that a driver might lose control of his bus as a result of a severe knock.

Councillor Neville Summerfield (Con, Brandwood) said Amey had been dragging its heels over repairs and patience was wearing thin.

He said: “We have waited several months for basic repairs to be carried out and feel totally ignored. Amey has promised to transform Birmingham’s roads and pavements and so far we have seen very little evidence of this.”

“I understand the bumps have cost them something like £4,000 so far and every day vehicles are coming back with knocks and scrapes. This is not just inconvenience, but a safety issue.”

National Express explained that the condition of the road surface has deteriorated to such an extent they have no option but consider diverting the service which travels from Birmingham city centre to West Heath via Moseley and Kings Heath.

A spokeswoman said that they are now having talks with the council contractor over the road.

“Safety is our number one priority and we have raised our repeated concerns around the condition of traffic calming measures. We look forward to the matter now being resolved swiftly.”

Mike Notman, project director from Amey, added: “We are aware of the enquiry regarding Allens Croft Road and we are working with the operations manager at National Express to resolve the issue.

“An inspector has attended the site with National Express to understand how we can work together to improve the situation. ”