LABOUR is heading for its weakest showing in local government for more than half a century. The party’s share of the vote in this week’s local, Scottish and Welsh elections is likely to be smaller even than when Michael Foot was leader in the early 1980s and it was hit by the Social Democratic party breakaway.

Labour’s performance in recent council by-elections, an accurate predictor of local election results, shows it trailing badly in third place with a national equivalent vote of 24%, according to an analysis for The Sunday Times by Colin Rallings and Michael Thrasher of Plymouth University’s elections centre.

Labour is down six points compared with the last time these elections were fought in 2003, before the “Iraq factor” had fully kicked in.

A 24% share of the vote in Tony Blair’s last election as leader would increase the pressure on him to step down quickly. This weekend he told journalists not to “hold their breath” for an announcement of his departure.

A YouGov poll of more than 1,100 Labour party members suggests that Gordon Brown, who is waiting on Blair’s announcement, does not face any serious groundswell of opposition from within the party. Asked who they would vote for in a leadership contest, 80% of members who said they would vote backed Brown, followed by 9% for John McDonnell, a left-wing challenger, 6% for Michael Meacher, a former environment minister, and just 5% for Charles Clarke, the former home secretary.

The poll suggests Clarke, who has not yet declared his intention to stand, would be humiliated in a straight fight with Brown, as would John Reid, now the home secretary.

Meacher will today say it is “imperative” that Labour has a proper debate about its future direction, not a Brown coronation.

“Gordon Brown is all in favour of competition in the public services. If he feels like that, why is the leadership of the Labour party the only area where he seems not to want a contest?” said Meacher, who is the most likely candidate to face the chancellor in a leadership contest.

Meacher confirmed he is in talks with McDonnell, his fellow leadership contender, over a deal to ensure there will be a challenge to Brown. This would see the candidate with the least chance of securing the necessary 45 nominations drop out of the race.

A closer contest is in prospect for Labour’s deputy leadership, according to the YouGov poll. Hilary Benn, the international development secretary, is ahead on 36%, followed by Alan Johnson, 19%; Peter Hain, 15%; Harriet Harman, 13%; Jon Cruddas, 10%, and party chairman Hazel Blears, 9%.

Although Labour strategists have all but accepted the party is heading for a drubbing this week, with a probable loss of 400-500 council seats, they will take comfort from the Rallings and Thrasher analysis, which suggests even a disastrous showing might not provide a clear signal that David Cameron’s Tories are heading for government.

The academics say the Tories require a national equivalent vote share of 42% or more to be firmly heading for No 10. A 38% showing, in line with the national equivalent vote in recent council by-elections, would suggest the party has made no progress over the past year and is only performing as well as when William Hague was leader in 2000.

Tory strategists have publicly dismissed claims that they hope to gain at least 600 council seats because they are anxious to avoid raising expectations. Privately, the party is understood to be aiming for a minimum of 800 gains, far higher than reported figures. According to Rallings and Thrasher, however, a 38% vote this week would give the Tories only 300-400 seat gains.

The Tories hope to boost their vote by challenging claims that Blair’s departure will mark a fresh start for Labour. In a speech today Cameron will say: “Blair may be going, but we know that it’s Brown who’s coming, the man who’s raised our taxes, wrecked our pensions and ruined trust in politics with his endless centralisation, meddling and spin. New leader, same old Labour.”

In contrast to the Tories, the Liberal Democrats under Sir Menzies Campbell could have cause for celebration. Their national equivalent vote share at local level (28%) would, if repeated this week, be the party’s best showing at local level.

For all the parties the challenge is to overcome public cynicism and apathy. Cameron has identified “the people in the staff room of an ordinary primary school” - dubbed Miss Staff Room - as the kind of voters the Tories have to win over. They appear interested but not yet convinced.

Kevin O’Donnell, 26, a primary school teacher from Woking in Surrey, said: “For me education is a high priority, as is global warming and the environment. I’m a floating voter, which makes me valuable. Labour’s been too dictatorial - I don’t believe the state always knows best. But when David Cameron says he wants the staff room vote he needs to be more specific about how he’s going to attract me.”

Downing Street has conceded that Labour is unlikely to win this week’s Scottish parliament election in the wake of a string of opinion polls putting the Scottish National party on course to emerge as the biggest party.

A source close to No 10 said: “The best we can hope for is we’ll get the same number of seats as the SNP. If we get that, Jack McConnell will be hailed a hero and paraded throughout Scotland.”

Senior Labour figures now regard a change of leader in Scotland as inevitable.

In a further sign that Labour is losing its grip on Scotland, Nicol Stephen, the Lib Dem leader and potential kingmaker of the next Scottish executive, has said he is ready to abandon Labour after eight years in coalition and side with the SNP. He said if the SNP were the largest party on May 4 he would enter talks with it first rather than sticking with Labour.

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