Water companies must tackle the 20% of water currently lost through leakage, some three billion litres a day, government must set new resilience standards and consumers should cut their usage from around 125 to 110 litres a day, Sir John said.

Doing so would reduce the "likely emergency measures which might be required" otherwise, such as "standpipes in the street, millions of plastic bottles of water being handed out, people facing hosepipe bans - all these things which are normally required in extreme situations" and are extremely expensive.