LONDON (AFP) - Voters in one of the country's most deprived areas are to vote Thursday in a by-election seen as the latest test for embattled Prime Minister Gordon Brown.

All eyes will be on whether Brown's governing Labour Party will see a haemorrhage of support in the Glasgow East constituency, or even lose in what has traditionally been its heartland.

Labour has lost two by-elections in recent months -- one a safe seat in northwest England and another where they trailed in fifth behind the far-right British National Party -- and is desperate to avoid another failure.

Brown is also under pressure because of the rising cost of living and has been criticised for his administration's recent economic record and his own leadership style that has led to talk of him being replaced.

One of his party's former spin doctors in Scotland has said that Brown, born and brought up in nearby Govan where his father was a church minister, will be challenged for the leadership if they are defeated in Glasgow East.

Opinion polls and political betting indicate that Labour will retain the seat, where it won a 13,507 majority at the last general election in 2005, but the party's margin of victory could be cut significantly.

A Progressive Scottish Opinion poll for the Scottish Daily Mail at the weekend predicted that Labour would win 52 percent of the vote, with the main challengers, the Scottish National Party (SNP), on 35 percent.

Compared to the 2005 general election, that represents an 11 percent fall for Labour and an 18 percent increase for the SNP, which won a narrow victory in 2007 to become the largest party in the Scottish Parliament in Edinburgh.

"If this poll is right, Glasgow East looks set to save Gordon Brown his job," John Curtice, a professor of politics at Glasgow's Strathclyde University, was quoted as saying by the newspaper.

SNP leader Alex Salmond, a keen horse racing fan who is also the First Minister in the minority government in Edinburgh, has said that "favourites don't always win" and has predicted a "political earthquake".

Glasgow East's boundaries have been withdrawn since the 2005 general election. A mainly inner-city seat, it has acute social deprivation in housing, employment and health.

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