The leader of Britain's main opposition Labour Party has ruled out forming a coalition government with the separatist Scottish National Party after May's national election.

Ed Miliband said Monday that such an arrangement "will not happen."

The SNP is expected to make big gains in the May 7 ballot, capitalizing in part on the grass roots organization put into place during last year's independence referendum.

The SNP could grab many of Labour's Scottish seats, making it hard for Labour to form a government.

Polls suggest no party has enough support to form a majority government, meaning some sort of multi-party alliance is likely.

Prime Minister David Cameron has called Miliband "despicable" for pondering a power-sharing deal with the party that wanted "to break up our country."