Lamont was a prominent figure in the Better Together Campaign, the cross-party political movement founded to keep Scotland as part of the United Kingdom following the SNP's announcement of a referendum on Scottish independence in 2014. She was outspoken in her opposition to Scottish independence, using a keynote speech at UK Labour's 2013 conference in Brighton to accuse the SNP of nurturing hostility between Scotland and the rest of the UK, and describing nationalism as a "virus that has affected so many nations and done so much harm". Lamont is in favour of greater devolved powers for the Scottish Parliament, and established a Commission to look at how this can be achieved.