LONDON (Reuters) - The head of Britain's opposition Labour party in Scotland has quit, unsettling the party in one of its heartlands ahead of national elections in May next year.

Ms Johann Lamont said in a newspaper interview that she was standing down with immediate effect, little more than a month after a referendum in Scotland when Labour and Britain's other national parties defeated a push for independence.

The Daily Record said Ms Lamont was unhappy about internal criticism of her and she hit out at the party in London, under leader Ed Miliband, for not allowing the Scottish wing of the party more autonomy.

Some Labour officials in Westminster "do not understand the politics they are facing", she told the newspaper, calling them "dinosaurs". "I am standing down so that the debate our country demands can take place," Ms Lamont said.

She was named leader of the Labour party in Scotland in 2011. Her decision to quit follows the resignation of Alex Salmond as leader of the Scottish National Party (SNP), which runs Scotland's devolved government, shortly after the Sept 18 independence referendum.

Labour has traditionally dominated Scottish politics and won 41 of Scotland's 59 seats in Britain's Parliament in the last national election in 2010.

The hopes of Labour leader Ed Miliband of becoming prime minister at the next election in May depend in part on the party's ability to see off the challenge in Scotland from the SNP.