After his election on 5 May 2005, then Liberal Democrat leader Charles Kennedy appointed Williams as the party's public health spokesperson, shadowing the public health minister Caroline Flint. In this role he served on the committee that scrutinised a health bill that introduced a ban on smoking in public places. Williams supported a ban on smoking in all public places, rather than an alternative proposal to exempt private clubs and pubs which do not serve food from the ban. He won an award from World Health Organization for his advocacy of a full ban. On 29 November 2005, Williams introduced a Ten Minute Rule bill to the House of Commons to reduce the voting age to 16. The motion was supported by a majority of Labour members and Liberal Democrats, but opposed by the Conservatives. It was defeated by 136-128 votes. In June 2006, Williams launched a campaign against homophobic bullying, after organising the education and skills select committee's first enquiry into bullying in schools.