Labour could lose nearly 2,000 councillors in May’s council elections, experts have warned.

Sir Keir Starmer’s party may shed more than three in five of its councillors who are up for election, Colin Rallings and Michael Thrasher said.

They forecast that the Prime Minister is likely to lose ‘well over’ 1,000 councillors if the pattern of local by-elections since May continues.

A loss of that magnitude would spell danger for the PM. He has long been predicted to face a leadership challenge if the elections go badly.

The Tories are also likely to face difficulties in postponed county council elections and ‘substantial’ Reform UK gains are inevitable, the experts said.

On May 7, 136 councils will go to the polls and 5,013 seats will be contested. Labour is defending 2,557 seats, the Tories 1,362, the Lib Dems 684 and independents and others 410.

In an analysis for the Local Government Chronicle, Mr Rallings and Mr Thrasher say Labour will be hit hard in May.

It will be battling Reform in northern metropolitan councils, while the Tories are vulnerable in county councils and some outer London boroughs, they said.

Labour could lose ‘well over’ 1,000 councillors – and nearer 2,000 if pattern of by-elections continues, say top pollsters

Their prediction comes after Reform won nearly 700 seats in last year’s local elections from a standing start, while the Conservatives lost two-thirds of the seats they were defending.

The pair said that this year, Labour was in the spotlight as it was defending more than half of the 5,013 seats falling vacant across 136 councils.

‘That dominance reflects the party’s strength in London and the metropolitan boroughs where it currently controls no fewer than 44 of the 64 councils with elections,’ they said.

‘A repeat of last year and Labour could be well over 1,000 councillors down.

‘Indeed, it has retained just a quarter of the seats being defended at local by-elections since last May, suffering an average decline of 25per cent in vote share.

‘A hit of that magnitude would see the party’s losses edging closer to 2,000.’

Labour is facing a ‘tough fight’ with Reform in metropolitan boroughs including Barnsley, Sandwell, Sunderland and Wakefield.

It is also likely to sustain a ‘double-pronged attack from its left’ in London from the Greens and pro-Gaza independents, they added.

‘Several councillors have defected from Labour to the Greens in recent months in places like Brent, Lewisham and Southwark,’ they said.

‘There and in north east boroughs like Hackney, Islington and Newham, Green gains may be expected.’

They noted that Labour’s approach to the Middle East ate into Labour support at the 2024 general election and was likely to ‘hurt the party again’.

The pair said that if Reform performs as well as it did last year, it would be likely to take control of Essex county council and be a significant presence in others.

The Tories, meanwhile, face ‘particular jeopardy’ in some seats and could lose seats to Reform, the pair said.

Kemi Badenoch’s party fared badly in last year’s local elections, losing two-thirds of the seats and overall control of the councils they were defending.

Meanwhile, Reform won nearly 700 seats from a standing start and a majority in 10 councils.

‘The Conservatives hold little more than a quarter of the overall vacancies but face particular jeopardy in the county contests postponed from 2025,’ they said.

‘It may be that support for Reform has plateaued, but given it won only three seats four years ago substantial gains from such a low base are inevitable.’