Brighton Pavilion MP Caroline Lucas presented Britain’s greenest universities with “first class degrees” at a “graduation ceremony” held in Parliament.
Brighton was ranked third in the league out of 145 universities and higher education institutions – up from 21st last year.
Sussex University was ranked 45th – up from 89th.
People and Planet, a student network campaigning to protect the environment, organises the Britain’s only independent ranking of universities for their environmental and ethical performance.
Dr Lucas, who gave out certificates alongside environmentalist Jonathon Porritt, said: “It’s really encouraging to see students and universities working together to reduce their carbon emissions and prepare for a green economy.
“The 40 universities being presented with their first class green degrees at today’s graduation ceremony in Parliament are a shining example of what can be achieved.
“However, universities must keep up this momentum and will need strong leadership from the government if we are to truly create a sustainable, higher education sector.”
Professor Stuart Laing, Brighton University’s deputy vice-chancellor, said: “This is outstanding news and reflects the hard work that staff and students are putting into making our institution more sustainable.
“The university is committed to sustainable development, environmentally and educationally, and to helping safeguard our planet for future generations.
“Protecting and renewing our shared natural and built environment is the greatest challenge facing our planet and all universities have an important part to play in meeting this challenge.
“Our aim at Brighton is to be a truly sustainable university in everything that we do.”
Professor Laing, who leads on cross-university sustainability and biodiversity actions, added: “Every year the Green League requirements get tougher but our continuous efforts mean we keep going up.
“We were at 50th place in 2007.
“Every area of the university is involved in the effort and every area is improving, including all faculties, estate and facilities management, residential and catering services, finance, human resources, and student services.
“All are essential and all deserve to be congratulated for their efforts.”
Brighton University aims to use Fairtrade products, seasonal and locally grown produce, free-range eggs and fish sourced from sustainable stocks.
Its sustainable food policy also aims to reduce the amount of bottled water being used.
The policy encourages waste reduction, sourcing and procuring more energy-efficient production equipment and a trial of food waste recycling.
Louise Hazan, People and Planet’s climate change campaigns and communications manager, said: “Congratulations to all the staff and students at the University of Brighton for their role in creating the third greenest university in the UK.
“Their success in integrating sustainability throughout the curriculum and finding creative ways to engage staff and students in the transition to sustainability is exemplary.
“National improvements across the People and Planet Green League results this year show universities are listening to the 70 per cent of students demanding greener degrees and that the university sector is leading the way to a low-carbon and sustainable future.”