The backers of a planned new Heathrow rail link fear it will not be completed until 2030.
The concern was raised by the independent Heathrow Southern Railway Limited (HSRL) on publication of strategic objectives for southern access to the London hub by the Department for Transport.
The DoT believes such a link will not be completed before 2030 as rail capacity is raised in phases.
The department also wants to consdier alternative transport options including light rail, bus rapid transit, guided busways, autonomous vehicles; or a combination of them.
“The increased passenger demand generated through natural growth and the construction of a third runway at Heathrow is not anticipated to increase as a step change but rather an incremental increase over a number of years,” the DoT said.
“With this in mind, government expects southern access to Heatbrow interventions to be delivered in phases over a period of time, increasing capacity to meet the required demand.
“We do not expect interventions to be completed prior to 2030.
But HSRL chief executive Graham Cross said: “We believe our scheme meets the DfT’s strategic objectives.
“Whilst their publication is welcome in showing the case for a new link, they no longer contain the certainty that this should be a conventional railway. Injecting uncertainty by considering experimental transport technologies largely untested in the real world will delay the commencement of this vital new public transport link.
“We believe conventional rail is able to carry the volumes of passengers necessary to meet the public transport mode share target in the Airports National Policy Statement (ANPS) passed by Parliament in 2018 along with the ANPS’s requirement to be open as soon as reasonably practicable after the third runway, currently projected for 2026.
“Whilst the DfT now envisages any link not being completed prior to 2030, our railway could be open and fully serving Surrey, Hampshire and South West London in 2026 if we start now.
“We urge residents, businesses and stakeholders to continue pressing for urgent progress on a Southern Rail Link to Heathrow to meet the existing air quality emergency, ease road congestion and reduce the current high levels of greenhouse gases from surface transport.”