In 2006, he was appointed as a LibDem shadow environment minister and championed changes to the Energy Act 2008 to promote renewable energy. Martin jointly tabled the key amendment to the Climate Change Act 2008 that strengthened the target for UK greenhouse gas emission reductions to 80% by 2050.
He also used the position to successfully champion animal welfare including the reduction of animal research, the banning of wild animals in circuses and the microchipping of pet dogs. His contribution was recognised when he was voted Animal Welfare champion 2009 by his parliamentary colleagues of all parties.
After he was re-elected in May 2010, Martin was appointed chair of the Liberal Democrat parliamentary committee on transport. He strongly supported the coalition's continued investment in public transport - and was particularly pleased when the 2011 Budget included funding for the recently completed redoubling of the Swindon/Kemble line which will improve services from Cheltenham to Swindon, Reading and London.
In March 2011, Martin become chair of the Liberal Democrat parliamentary committee on international affairs, this time linking to coalition ministers in the Foreign Office, Department for International Development and Ministry of Defence. He strongly supported the government's historic achievement of the 40-year old target of spending 0.7% of gross national income on development assistance. In foreign policy, he has called for more action to curb British and international arms sales to countries with no track record of respecting human rights or democracy and strongly backed the International Arms Trade Treaty in 2013. He has cautiously supported UK military involvement overseas when there is a strong legal and humanitarian case, clear regional support, a long-term plan and explicit approval from Parliament. Tony Blair's invasion of Iraq in 2003 would have failed three out of four of these tests.
In the 2010-15 parliament, Martin promoted two private member's bills of his own. In 2011, he called for a statutory code of practice for local pubs to level the playing field between landlord and the big pub-owning companies. Although the bill was lost, Lib Dem ministers Jenny Willott and Jo Swinson backed the idea and it is now becoming law. The second bill called for more action to prevent irresponsible and dangerous pavement parking.
You can watch Martin proposing his pub bill here.
Martin also held posts in several all-party parliamentary groups: he was an officer of both the associate parliamentary group on corporate responsibility and the all-party parliamentary group on responsible investment, both of which encourage companies to improve their social, ethical and environmental performance. He was the chair and founder of the all-party parliamentary group for tribal peoples and an officer of all-party groups promoting environment and development, employee ownership and education.