Martin scraped through one confidence vote in May

The decision by the New Democratic Party raises the possibility of a confidence vote and an early election, analyst say.

The New Democrats said they could no longer back the government following a row over private health care spending.

Mr Martin's Liberal government, which narrowly won re-election in June 2004, survived a no-confidence vote in May.

Crucial support

The Liberals had promised to invest heavily in social spending in return for the New Democrats' support in the confidence vote.

But New Democrats leader Jack Layton withdrew his support saying the government appeared unwilling to stop the increased use of private heath care.

"We cannot express confidence in a government unwilling to act on such a critical issue," Mr Layton said.

The government has been under pressure amid allegations of irregularities over public advertising contracts awarded during a previous administration in the 1990s.

Mr Martin is not implicated in the scandal, but the opposition says his government is corrupt and should be forced out of office.

The earliest opportunity for a confidence motion will be on 15 November, with a vote possible on the following day.