Ministers are under pressure to end the “postcode lottery” on water by introducing a single social tariff for households on low incomes, amid fresh signs consumers are struggling to keep up with bill payments.

Water companies in England and Wales offer their own social tariffs, providing discounts to consumers on low incomes. However, some of the schemes are more generous than others, creating vast disparities in how much consumers pay in different regions. 

Campaigners have argued that a central funding pot into which all water companies pay would help more people.

In a letter to the minister for water and flooding, Emma Hardy, seen by the Guardian, 14 charities said the new government had a “huge opportunity” to help people in poverty with their water costs.

The charities, including Independent Age, Money Advice Trust, Parkinson’s UK and Age UK, said such an initiative would “make a tangible positive difference to the lives of people of all ages living on low incomes”.

They wrote: “A single water social tariff would be a simple way to provide fair and consistent support for people in financial hardship, helping ensure more people are able to access the water they need without having to make extreme sacrifices.”

The Guardian reported last year that, under the previous Conservative government, officials had been positive about the idea of a uniform social tariff but backed away from it after examining the issue in detail.

It is understood that water industry representatives have now raised the idea with the Department for Environment, Food and Rural Affairs (Defra) and discussions are continuing.

The water industry has faced widespread criticism over sewage dumping, debt levels, executive pay and underinvestment.

Sources said some companies had previously resisted a single social tariff as it would mean they were in effect subsidising companies in other regions that needed to make larger investments.

Research conducted by YouGov for Independent Age found that, in England, 38% of people aged over 65 on household incomes below £15,000 struggled to keep up with their water bills. In Wales, the figure was 29%.

Val Thomas, 77, from Essex, said she had reduced her water usage. “I am now so worried about using water, even though maintaining good hygiene is important for my health condition, that I have cut back on water use a lot,” she said. “I only shower on alternate days and never use my bath.”

Campaigners had hoped a uniform social tariff could be devised before the next water industry price review period, which runs from 2025-30.

However, submissions have already been made for that review, and last month the industry regulator, Ofwat, provisionally said average water bills would increase by 21% over the next five years from April 2025.

Independent Age’s chief executive, Joanna Elson, said: “We regularly hear from people in later life who are cutting back on washing and laundry to lower their bills to a more affordable level; this isn’t the later life any of us would want.

“We’re urging the new UK government to take swift action to end the unfair postcode lottery by introducing a single social tariff for England and Wales. An address shouldn’t impact how much support someone in financial hardship receives towards their water bill.”

Separately, research by Citizens Advice found up to a quarter of the UK population believed they might have to turn off their heating and hot water this winter because of rising energy bills. This increased to 31% for households with children and 39% for people on a low income, the survey found.

The energy regulator, Ofgem, is expected to say on Friday that energy bills across Great Britain will rise by 9% from October to an average of £1,714 a year.

Defra said: “We expect water companies to have robust support in place for customers that are struggling to pay their bills, including bill discount schemes and financial support plans.

“For too long, investment has not kept pace with the challenges of an ageing infrastructure system, a rapidly growing population, and climate change. It is not fair that customers should suffer the consequences of years of mismanagement.”