Thames Water has already been given the green light by Mr Reed to build a water recycling plant in Teddington, west London, which would treat sewage from the Mogden Sewage Treatment Works in Isleworth before pumping it back into the river. The plan was designated an NSIP in January under the previous government.

The treated wastewater would be used to replace water extracted from the river to keep the supply replenished during droughts.

The plans have been opposed by Richmond Council, which claims it could adversely affect water quality and local open spaces.

Campaigners say sewage treatment does not permanently eliminate pollutants such as chemicals or microplastics, which can threaten biodiversity in stretches of the river.

Reed launched a major overhaul of the water industry this week, warning of the need to increase supply.

“By the mid-2030s if we don’t take steps to increase water availability – reservoirs as well as infrastructure – the demand for drinking water will start to outstrip supply, in a way that is already happening in some Mediterranean countries,” he said.

“We cannot allow the water system, the water sector, to continue in this way.”

A Defra spokesman said: “Our water infrastructure requires significant investment and development to secure supplies as we adapt to climate change and a growing population and to help grow the economy.

“All nationally significant infrastructure projects need development consent, under the Planning Act 2008, before plans can proceed, ensuring proper consultation with local communities affected by a new scheme takes place before a development consent application.”