Bulding the infrastructure for new communities in two of the Communities Plan's housing growth areas will cost Kent £4.2bn, the council has calculated.
Planners say the schools, transport links and hospitals needed to support an extra 30,000 homes in the Ashford growth area would cost £1.15bn.

And they estimate the infrastructure bill for an extra 35,000 homes in Kent Thameside, centred on Dartford, Gravesham and Swale, would top £3bn.

In total, Kent is expected to deliver an extra 116,000 homes by 2021.

The full cost of this is expected to be £7.5bn, which would cover 120 new primary and secondary schools, a new reservoir, extra health and social care facilities and improvements to road and rail infrastructure.

Council leader Sir Sandy Bruce-Lockhart said: "We are demanding cast-iron guarantees of the necessary funding for the infrastructure. It's not an exaggeration to say this is the biggest peacetime challenge to face Kent. If government gets it wrong, the mistakes cannot be rectified."

The council, rated "excellent" by the Audit Commission, plans full coordination between housing, transport, education and planning departments to meet the challenge.

Geoffrey Clifton-Brown, Conservative shadow minister for planning, said: "The government needs to ensure total sign-up from five major departments on this [but] John Prescott has so far failed to get any sort of guarantee whatsoever."