Walking and cycling holidays take on a new meaning at Forster. For every journey to and from work that is made by foot or bike, employees earn five minutes' holiday, which can add up to a total of 2½ extra days a year.

The company helps budding walkers and cyclists find route maps, has organised cycle confidence sessions, and helps them link up with colleagues who live locally. A quarter of staff are reaping the rewards of these initiatives, which not only cut emissions, but also have health benefits.

A top green score of 98% shows that people at Forster don't associate being green with beards and sandals. They believe the organisation is getting better at protecting the environment (another 98% result) and receive regular communication on green issues (88%).

"It's important to be open and report back on results when we do well, and when we don't do so well. You've got to be open to ideas," says office manager Joanna Foy. "You've got to have a delicate balance — understand people's needs and make it easy for them to follow the initiatives."

The London-based firm brands itself an "ethical marketing, PR and design company". Its aim is to use communication for positive change in health, social justice and the environment. Recent work includes the Frank campaign to inform young people about drugs, promoting a change in attitude towards young mums and raising awareness of Fairtrade products.

Environmental commitments are at the heart of how the organisation operates (94%), both in terms of the campaigns it works on, and its day to day running. This was always the intention when chief executive Jilly Forster set up the firm 13 years ago. "It was a founding principle from the start," she says. "It's part of my DNA."

This is clear to see, according to employees, who believe their boss is committed to the environment (97%, a top score). They know it is a high priority for Forster — a 99% score beats every other company in the list. A perfect score of 100% shows that bosses don't expect the workforce to save the world while they drive gas-guzzling cars.

"It has helped us financially as well as acting as a glue to hold us together," says Forster. "I think it's the only way a business can be run. I know that it's a win-win situation. Businesses assume that it's going to cost a huge amount, but it doesn't."

Progress against the firm's environmental policy is communicated regularly (93%). In 2006-7, the amount of paper purchased was reduced by 8%. Electricity is bought on a green tariff, and the aim for 2008-9 is to achieve ISO 14001 certification.

Although the message comes from Forster and the leadership board, every member of staff plays a part. Quarterly company days are an opportunity to brainstorm ideas to improve the firm, including its environmental performance. Employees are encouraged to get involved and are happy to use their initiative. For instance, two keen cyclists arranged for bicycle stands to be installed outside the office by writing to Southwark council.

A 91% top score shows people are encouraged to get involved with the community. Full-time staff are allocated 40 hours for volunteering every year.

"It goes beyond 'green' as a tight definition. It's giving something back and being sustainable," says communications consultant Amy Meadows. "We just have a sustainable approach to everything we do. We work with local suppliers, even down to ordering sandwiches. We try to think local." Staff award the firm another top score of 98% for supporting local suppliers.

The environment is an everyday consideration at Forster (95%). Job descriptions incorporate being environmentally responsible, and this message isn't forgotten amid heavy workloads and deadlines.

"The best way to persuade people is to make it easy, fun and relevant. That informs every aspect of our environmental policy," says Peter Gilheany, director and head of public relations and advocacy.

Instead of telling staff to turn the heating down, in the colder months they are equipped with winter survival kits, which include hot water bottles, jumpers, wool and knitting needles to make scarves.

"It doesn't work if you just say 'do it'. If you have a sign, it soon becomes wallpaper," says Forster. "You need people to understand. It's about making it real. That's when the penny drops."

Air conditioning isn't used too much during the summer (98%), and employees feel they have the power to influence the organisation's energy usage (83%). A 96% score shows people at Forster think green.

Promoting positive change is Forster's raison d'être, and the company is walking the walk when it comes to the environment. "We're probably ahead of the game, but it's our business to be," says Gilheany. "Nothing we've done is revolutionary. Anyone can do what we do." But judging by its top-rank debut, nobody is doing it as well as Forster.