Scotland's working class voters are deserting New Labour, according to a study by leading Scottish academics.

The findings in the Scottish Parliamentary Election study show a sharp drop in support in traditionally strong labour seats since the last general election.

In a study which compared voting patterns in the 1997 General Election and the 1999 elections for the Scottish parliament, researchers found that labour's support in its traditional working class core voters had fallen by 16% in those two years.

The Scottish Parliamentary Election Study was funded by the Economic and Social Research Council and relies on interviews with voters.

The electoral experts who analysed the information found that, while support among middle class labour voters appears to be holding up, there is a lack of enthusiasm among traditional constituencies and that support has fallen most steeply in previously strong labour seats.

The results - which are due to be presented to a conference in Edinburgh this week - are bound to intensify the debate over whether Labour should pay more attention to its core vote in the run up to the general election.

The figures are bad news for the party's leadership in Scotland, coming just before the campaign for the Ayr by-election begins in earnest.

The marginal seat was won by 25 votes by Labour from the Conservatives. The sitting MSP, Ian Welsh, resigned in December, saying he was spending too much time away from his family.

Voting will take place on 16 March.