Up to 100 of the UK capital’s pub­lic-sector office buildings, including City Hall and Transport for London’s headquarters, are to be given a green makeover at a cost of about £10m.

Ken Livingstone, the London mayor, will on Friday invite energy and utility management companies to bid for the contract to increase en­ergy efficiency in the buildings by about 25 per cent.

London is the first to take action of 16 cities, including New York and Tokyo, which in May signed up to a deal, developed by the Clinton Climate Initiative, to make buildings more efficient.

The contract is seen as the first phase of creating a framework that could be opened up to include the whole of the public sector.

The mayor wants to prove that increasing the efficiency of large buildings cannot only cut carbon emissions but also achieve cost savings. If successful, it is hoped the contract will be copied by the private sector.

The 900 buildings run by the Greater London Authority group, which includes TfL, the Metropolitan Police Authority, London Fire Authority and London Dev­el­opment Agency, could save up to 50,000 tonnes of carbon emissions and £1m in lower energy bills each year.

The contract will build in guarantees of energy savings over a 10-year period.

The mayor’s advisers be­lieve the contract can pay for itself over time and could stimulate a new market in improving energy efficiency in corporate buildings.

They say a contract to conduct an audit of scores of buildings to determine the best way to improve each one makes more sense than making piecemeal improvements, such as adding ­double glazing, without an overall plan.

Mr Livingstone said: “London is leading the way by becoming the first of the 16 cities signed up to the Clinton Climate Initiative programme to begin work to cut climate change emissions by making our buildings more energy-efficient. We have started the tender process for companies to bid for the first part of the work and I hope that this will also lead to a boost in London’s green industries.”

Under the terms of the contract, the companies will have to plan and implement energy-saving measures for each building, possibly ranging from reducing heat gain and installing energy-efficient lighting and better insulation, to adding “smart” controls for buildings’ services and even sustainable energy systems.

The mayor’s office is expecting international interest in the contract, which is being advertised in the Official Journal of the European Union. Inter­national groups such as Honeywell and Siemens have expressed interest in the work for all 16 cities.