Alexander Dennis, Britain’s biggest bus maker, is stepping up efforts to design a new version of the popular Routemaster bus for London, based around low-energy drive technology such as the use of novel “hybrid” engines.

Colin Robertson, chief executive of the Falkirk-based company, said 80 development engineers were devoting more time to the Routemaster project, following the call by Boris Johnson, the London mayor, to come up with a replacement for the vehicle by the time of the London Olympics in 2012.