Whitehall has hailed its employees as champion energy savers, revealing that central government departments have slashed carbon emissions by 13.8 per cent in a year, far exceeding the coalition’s promise to cut emissions 10 per cent during its first 12 months in office.

Prime Minister David Cameron revealed the figures today and set a new target to cut emissions by 25 per cent by 2015, including emissions from government travel – a move that could result in banning ministers and civil servants from travelling business class.

DECC believes that savings throughout government cut energy bills by £13m over the past year.

Cameron hailed the achievement but urged ministers and civil servants to accelerate their efforts further to ensure the coalition achieves its much scrutinised goal of becoming “the greenest government ever”.

“We need to do more to stamp out energy waste in Whitehall, and make it easier for people and business to use energy more efficiently,” he said. “That’s why I’m committing the government to go further by reducing emissions by 25 per cent by 2015.”

Energy secretary Chris Huhne said the results show the government is leading by example. “When we promise to cut carbon, we mean it,” he said. “This is only the start and we’ve now got to get on and slash Whitehall’s emissions by a quarter by the end of this Parliament.”

Angela Bryant, director of the 10:10 campaign which originally prompted the government to sign up to the 10 per cent target, hailed the success of the initiative. “Today’s announcement shows what’s possible when you aim high,” she said. “10:10 organisations have proved this time and time again, but what’s crucial now is that these achievements inspire greater ambition for the country as a whole.”

The news came as the government confirmed it will run a series of trials from September in partnership with DIY retailers, local authorities and utilities, designed to encourage a greater uptake of energy efficiency measures and lay the ground work for next year’s Green Deal energy efficiency loan scheme.

B&Q and Sutton Council will consider offering a subsidised loft clearance service to test whether removing the “hassle” factor of insulation motivates people to make efficiency improvements.

The unwanted contents of the loft clearance will be donated to local charities. B&Q will also test the impact of offering collective purchasing discounts to households that buy energy efficient products.

Meanwhile, Homebase and Carillion will team up with a local authority to test the impact of offering upfront rewards to residents who purchase energy efficiency measures. The offer will include a one-month council tax holiday, or vouchers to spend in store.

First Utility and Opower will also carry out a trial to investigate the effect of behavioural feedback, including comparative consumption data, on consumer energy use.

In addition, DECC will launch a new design for the front page of the Energy Performance Certificate in April 2012, highlighting the information most likely to motivate people to cut energy use.

DECC predicts the impact of the new design could be considerable because nearly 1.4 million certificates were issued in the past 12 months.

Finally, the government announced it is to launch a new Responsibility Deal, inviting businesses to make a public commitment to reduce energy use a set amount by a specific date.

The voluntary scheme will formally launch in the autumn and is part of a broader approach by the government to establish new partnerships with business to achieve social objectives.