A glance at the West Midlands, the political barometer of Great Britain, underlines the huge challenge the Conservative Party faces to avoid a third successive General Election defeat.

Michael Howard requires an average swing against Labour across the entire country of 10.5 per cent to secure an overall majority of just one seat in the House of Commons.

Such a switch in voter loyalty would be unprecedented in modern times and few observers think it remotely likely, particularly given the Tories' inability to reach much more than 35 per cent in opinion polls since 1992.

The seats to watch out for in the West Midlands on election night - the constituencies the Tories simply have to win to get anywhere near an overall Commons majority - include Dudley South, where Northern Ireland Minister Ian Pearson has a 6,817 majority. His Conservative opponent requires a 9.5 per cent swing to take the seat.

At Halesowen and Rowley Regis, Labour's Sylvia Heal will be safe unless there is a swing of 9.9 per cent to the Conservatives.

More realistically for the Tories, Birmingham city councillor Deirdre Alden needs a 6.4 per cent swing in Edgbaston to unseat Labour MP Gisela Stuart.

A victory for Coun Alden would be hugely symbolic for a party that has long been embarrassed by having only one of Birmingham's 11 MPs. And the swing needed to pick up Edgbaston would, if repeated nationally, enable the Tories to pick up dozens of constituencies, cutting Labour's Commons majority to under 50.

Warwickshire, in common with Edgbaston, used to be territory the Conservatives took for granted. But since Labour's historic 1997 election victory the Tories have been unable to make any headway in the south of the county.

All eyes will be on Rugby and Kenilworth, where Labour MP Andy King, with a 2,877 majority last time, faces defeat if the swing to the Conservatives exceeds 2.7 per cent.

In Worcestershire, Trade and Industry Minister Jacqui Smith has a majority of 2,484 in Redditch and will be out if the Tories manage a 2.9 per cent swing.

Failure by the Tories to win seats like Rugby and Kenilworth and Redditch would see Tony Blair returned with a thumping majority, while raising doubts about Michael Howard's leadership.

Only if the Tories can produce a swing of four or five per cent - picking up seats like Stourbridge, The Wrekin, and Warwick & Leamington - is Mr Howard's position likely to be secure. Lib Dem hope to hold on to a number of marginal seats in the Midlands, while possibly picking up several more off the back of disenchantment with Labour over the Iraq war.

John Hemming, the Lib Dem deputy leader of Birmingham City Council, requires a 4.4 per cent swing to win Yardley, where former Labour Education Secretary Estelle Morris is not standing again. In Worcestershire West, Tory MP Sir Michael Spicer is vulnerable to a Lib Dem swing of 6.6 per cent.

The Tories, meanwhile hope to eat into Lib Dem territory with their eyes on Hereford and Ludlow where a swing of less than two per cent is required for victory.