LONDON — Charles Kennedy, a former leader of the Liberal Democrats in Britain whose career was marked by success and tragedy, was found dead Monday at his home in Scotland. He was 55.

His family announced the death on Tuesday, and the police said there did not appear to be anything suspicious about it. The family said there would be an autopsy.

Mr. Kennedy was a popular and unpretentious politician who led the Liberal Democrats from 1999 to 2006 and opposed Britain’s involvement in the Iraq war. He resigned as head of the party after acknowledging that he had a drinking problem.

He did not abandon political life, however. He represented a constituency in northwest Scotland until he lost the Parliament seat last month to the Scottish National Party, which won all but three of Scotland’s 59 seats in the general election.