The leader of the Scottish Labour party, Kezia Dugdale, will address the shadow cabinet this week about the party’s desperate plight north of the border, amid growing tensions about tactics ahead of the crucial 5 May elections in Scotland, Northern Ireland, England and Wales.

Senior shadow cabinet figures believe Labour leader Jeremy Corbyn’s team is adopting a deliberate, self-defeating strategy of downplaying Labour’s prospects and is, in effect, raising the white flag in advance, to minimise criticism if and when it suffers damaging losses.

They insist that negative briefings about Labour’s chances everywhere but in the London mayoral election – where there is optimism that Labour’s Sadiq Khan will defeat Tory candidate Zac Goldsmith – make a nonsense of claims by Corbyn, after the Oldham byelection in December, that the party is enthusing a new generation of voters who have engaged with his “new politics”.

At their meeting last Tuesday, shadow ministers were briefed by officials about likely losses. They were told that the party is on course to lose every one of its remaining constituency seats in the Scottish parliament, and cede control of at least 16 councils in England, as well as effective control of the Welsh assembly. Corbyn’s allies are stressing that the last time the same seats were contested in England, in 2012, represented a “high-water mark” for Labour under Ed Miliband in the aftermath of George Osborne’s “omnishambles” budget, and that Labour cannot realistically expect to improve on those results.

The gloomy prognosis given to the shadow cabinet is borne out by analysis today for the Observer by Robert Ford, senior lecturer in politics at the University of Manchester, who says Labour could lose all 15 of its remaining constituency seats in the Scottish parliament as the SNP strengthens its grip. Based on the most recent polling, he calculates that Labour is 11% down on its 2011 levels of support, while the SNP is up 8%.

“A result in line with these polls would see 13 constituency seats fall to the SNP, while two further seats would be tight races between the SNP and the Conservatives with Labour coming third,” said Ford.

“Labour’s position may be even worse than the aggregate polling suggests, as their safest remaining seats tend to be in areas such as Glasgow and central Scotland, where swings to the SNP in the general election were largest ... A constituency wipeout for Scottish Labour in 2016 would complete an extraordinary political collapse for a party which dominated Scotland at all levels just a decade ago.”

These losses, he says, may be offset by increases in their regional list seats. “However, Labour have problems here too, as polling points to a much more fragmented regional vote, with rises for the Conservatives, the Greens, Ukip and the Liberal Democrats in current polling, while Labour and the SNP are in retreat.

“Labour could fall to 25 seats or below, far behind the SNP, who could claim up to 70, and only a little way ahead of the Conservatives, who could take 20 or more.”

In English councils, Labour is down on average by 8% on its 2012 polling levels, suggesting the loss of control of 20 councils, while in Wales a 7% fall in support since 2011 suggests that Labour would lose effective control of the Welsh assembly and could suffer its worst ever result there.However, with Dugdale likely to stress that Labour is rebuilding its organisation after losing 40 of its 41 Scottish seats at the general election, there is concern within the shadow cabinet and across the parliamentary party that the “spirit of Oldham” has been abandoned in favour of a negative “prepare for the worst” strategy to protect Corbyn.

Ian Murray, the shadow Scottish secretary, said: “There is a danger that we will do badly based on constant discussion of the latest opinion polls rather than by campaigning enthusiastically on the messages that people care about.”

Several other shadow cabinet members said the leadership seemed to have a “gloom-and-doom” message, while at the same time claiming to be making strides with the “new politics”. One member said: “We are either on the march as Jeremy Corbyn says, or we are not. Which is it?”

Graham Jones, the MP for Hyndburn, said it was the duty of everyone in the party to fight to win, not to predict or prepare for losses. “If we are saying we are going to lose huge numbers of seats, it is like going to into battle saying you are going to be slaughtered. If you are taking that approach, you should not be doing the job.”