About 1,000 London buildings including the Houses of Parliament and the National Gallery could soon be warmed by low-carbon heat sourced from the River Thames, London Underground and sewer networks.

Plans to develop the UK’s biggest heat network to supply decarbonised heat to buildings across Westminster were set out on Wednesday by the government as part of its pledge to back seven heat network zones with more than £5m of public funding.

The plan will involve a network of pipes constructed to carry excess heat captured underground to power hot water and central heating systems in the area.

The £1bn scheme will be developed by a joint venture – between heating specialists Hemiko and Vital Energi – known as the South Westminster Area Network partnership, designed to save the area about 75,000 tonnes of CO2 each year, the equivalent to planting 1.2m trees.