The water company has revealed it plans to invite tenders for the long-awaited capacity upgrade next month. Ahead of this, it will hold an online bidders briefing on 10 September to set out its plans to improve the quality of effluent released at the works and increase the site’s capacity.

Works will include trebling storm tank capacity, increasing sewage treatment flows by 80% and raising power supplies.

The decision to begin contractor selection comes as Oxford City Council launched a stinging attack against the embattled water company for holding up development across the county.

Councillor Susan Brown, leader of Oxford City Council, said: “We have long been raising the major problems created by the historic lack of investment by Thames Water in the Oxford Sewage Treatment Works, and its subsequent lack of capacity.

“This lack of investment has now led to the Environment Agency objecting to both the City Council’s proposed Local Plan 2040, and to housing and commercial planning applications coming forward in and around the city.

“This is a very significant environmental and economic issue for both Oxford and Oxfordshire.

She added: “Protecting and improving the water quality in our rivers and streams is fundamental, as is having adequate water supply and sewage capacity.

“We need to have the right infrastructure in place to do this. The fact that we do not, and that this is now also preventing or delaying the delivery of much-needed new homes and job opportunities, is a source of huge frustration and anger.

“We have been raising these issues locally for many years but have seen no action. While I am clear this is a failure of the previous government’s making, I have been greatly encouraged by the engagement shown by the current government on this issue.

“We are now engaged in active and constructive talks with Thames Water’s new chief executive, the EA, and the Water Services Regulation Authority.

“We have also entered a three-way agreement with Thames Water and the EA to work together to help address the planning issue as part of our draft Local Plan.

“It is clear from these discussions that there are shared objectives from all partners to support the sustainable development and growth of Oxford and the surrounding area; to focus on ensuring the necessary infrastructure is in place to protect and enhance the local environment; and to give assurance to the development community that the works will happen in a timely fashion to ensure we continue to deliver much-needed new homes and jobs.

“We also understand that Thames Water is working at pace with the relevant regulators to develop and put in place solutions that seek to address the situation.”

Email Thames Water for place at online teams supplier briefing.