The high-street giant Marks & Spencer is to encourage customers to reduce energy use by recommending a 30C wash on the labels of three-quarters of its clothes, it announced today as part of a wider climate change campaign launch.

The retailer said a 30C wash would save around 40% of the energy used in each laundry cycle, and that independent tests showed around 70% of its clothes could be washed effectively at this temperature.

The supermarket chain Asda replaced the 40C recommendation on all of its George garments several months ago and a spokeswoman said today that there had been no negative feedback from customers following the change.

At M&S the current recommended maximum temperatures will still appear on the labels, but they will be alongside the words: "Think climate - wash at 30C". The same advice will be provided on in-store leaflets, in advertising and on the company's website.

The new labels will begin to appear over the next few months.

The company, which has committed £200m to making its business more environmentally sustainable, said some of its products would benefit from a higher temperature wash, including bedding, towels, sportswear and underwear, as well as any items that were stained.

The chief executive, Stuart Rose, said he was aware that customers were concerned about climate change and wanted to minimise their impact on the environment.

"This is why we are encouraging our customers to wash their clothing at 30°C. It is a small change, but it can make a very big difference," he said.

"If we all moved to washing at 30C we could save enough electricity to light every street lamp in the UK for 10 months."

The initiative has been developed as part of the We're in This Together campaign, which is led by the Climate Group and brings together businesses, government and non-government organisations to help households reduce their emissions by one tonne over three years.

Companies to have signed up to the campaign include M&S, B&Q, Barclaycard, British Gas, 02, Royal & SunAlliance, Sky and Tesco. Other companies, including HSBC and National Express, will join later in the year. Collective reductions in emissions will be calculated and shown on the campaign website Together.com.

The Climate Group said that if every British household took part in the initiative, up to 25m tonnes of CO2 could be saved, which is more than the combined emissions of Scotland and Wales.

Steve Howard, the group's chief executive, said the success of the campaign would rest on reaching as many people as possible and "not just the usual audience for green initiatives".

The prime minister, Tony Blair, said at today's campaign launch that the government would continue to take the lead in tackling climate change, both at home and internationally.

"By working together - as individuals, businesses and nations - we can meet this challenge and safeguard our way of life and our planet," he said.

The environment secretary, David Miliband, who also attended the launch, said it had the full support of the government.

He told Sky News: "Different people in different ways can make their contribution across the three key areas of electricity, heat and transport.

"Individuals want to play their part and, if it helps their wallet too, we should support them to make the right decisions."