Gatwick Airport has insisted that water it poured into the River Mole on Christmas Eve to stop its runway flooding did not cause unprecedented flooding further downstream.

An airport spokesman explained that rainwater from the airfield was channelled into a balancing pond where two screw pumps moved it into a separation chamber before it was discharged into the Mole.

Flooding that day at Leatherhead, 20 miles downstream, reached levels never previously recorded, causing evacuations, ruined properties and closed roads.

But the spokesman said only "safe levels" of water were discharged in line with limits and guidance from the Environment Agency which monitors the river.

He said: "Our balancing ponds were absolutely not the cause of flooding further down the river. When they (the rivers) are flowing quickly it is safer to put more water in. There was no problem operating the balancing ponds at all.

"The whole problem was the sheer volume of water. We operate under an Environment Agency permit and we have to meet all their regulations. We did everything we could."

He said that a third screw pump, at the pond known as D, was never turned on, adding: "We never got to that so we were discharging at safe levels."

When floods struck again last Friday night he said one screw pump was turned on as a precaution but the water never reached the level needed to operate it.

The spokesman did not know the volume of water discharged on Christmas Eve but said not releasing any water at all was not an option.

He said: "It was impossible. If we did not release any at all, the high risk was the runway would have flooded."

He said there were six balancing ponds at Gatwick but only pond D, in the southeast near the Mole, took floodwater off the runway.

Flood victim Nik Cookson, who is forming the River Mole Action Group, said he still wanted to know how much water Gatwick Airport had let go from other balancing ponds.

He said: "What did they let go and what do they have that isn’t only this or only that. It doesn’t really seem to hold water.

"We need to know what they let go from how many ponds in what amounts. It succeeded in making the river behave in a way that it does not normally behave."