Andy White, senior leader of CCW, said it was good that more people than ever were being helped by social security payments.

“But it also shines a light on the fact that there are significant differences in the support available to customers depending on who serves them as a water company,” he said, describing it as a “postcode lottery”.

“Whether you actually get help and qualify for it, and how much help it is, depends entirely on what scheme each company offers,” he said.

“And we don’t think it’s right that people should have different support depending on where they live.”

CCW wants companies to have a social tariff for people who can’t afford their water and for everyone to contribute to a shared pot so that costs don’t fall heaviest on the poorest areas.

Water UK, which represents water companies, said: “Ultimately it is up to the government to set social tariff guidelines, but water companies offer significantly higher cuts than other utilities such as energy.”

The government said it was committed to supporting vulnerable consumers with their bills and tackling water poverty, and had announced “an independent water commission which will report back next year with recommendations to protect customers”.