Polls have closed in elections across Scotland, Wales and parts of England that could prove a decisive moment in Keir Starmer's leadership.
Labour is expected to suffer heavy losses throughout the country as the party languishes in the polls and faces challenges from Reform UK to the right and an insurgent Green Party to the left.
Polling guru Robert Hayward has suggested Labour could lose some 1,850 councillors in England.
The party is set to lose the national vote in Wales for the first time in more than a century, while in Scotland the SNP appears likely to remain the largest party.
As polls closed, deputy prime minister David Lammy said the elections had been "tough".
"I don't want to sugarcoat it, the message from the doorstep is this is a tough election cycle.
"This is a mid-term set of elections with people concerned about the cost-of-living and wanting to see the government go faster with quicker pace," he said.
Mr Lammy added that while Labour had run a "positive campaign", the party's "message of delivery" had been "drowned out by the politics of grievance".
A national drubbing is also likely to reignite speculation about Keir Starmer's leadership of the party and the country.
Before polls closed, The Times reported that Energy Secretary and former Labour leader Ed Miliband has privately urged the prime minister to set out a timetable for his departure after the elections.
Other cabinet ministers are said to be considering leadership tilts, including health secretary Wes Streeting and former deputy prime minister Angela Rayner.
Allies of Ms Rayner are confident she would be able to gain the support of the 81 MPs required to launch a challenge - a number which Mr Streeting is also said to have met, though neither are said to want to be the first to move.
Greater Manchester mayor Andy Burnham, who is said to have a plan to return to Westminster within weeks, has dropped out of giving a speech tomorrow morning.
Mr Burnham had been expected to address the second annual Festival of Childhood in Manchester on the morning after the elections, but this evening organisers said he had been replaced by Caroline Simpson, group chief executive of the Greater Manchester Combined Authority.
Meanwhile, Nigel Farage's Reform UK is set to make significant gains, building on last year's local elections that saw the party pick up almost 700 councillors and take control of 10 authorities.
The Greens are also expected to do well, with new leader Zack Polanski predicting "record-breaking local elections" for the party, while Ed Davey's Liberal Democrats are eyeing an eighth successive year of local gains.
But it could be another bad night for the Conservatives despite an improvement in party leader Kemi Badenoch's approval rating, with the party expected to lose further ground to Reform.
