80%
True

Thames Water is allowed to [pump sewage into rivers] under rules that are laid out in the Water Act of 1991.

The Water Industry Act 1991 is the principal statute governing water and sewerage companies in England and Wales and Ofwat's regulatory and enforcement powers. The MP's reference to the '1991' framework is correct (its precise title is the Water Industry Act 1991).
Checked Wed 1 Jul, 09:58 · Broadcast: PMQs: Prime Minister's Questions - 25 March 2026

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