Sir Keir Starmer is attempting to exploit the row over the 1% NHS pay offer in elections on "super Thursday", by claiming "a vote for Labour is a vote to support our nurses".
He is launching his party's campaign for elections in England, Scotland and Wales on 6 May, the biggest poll since the general election - with almost 40 million people eligible to vote.
The Labour leader will claim a vote for Labour, which has suffered a slump in support in opinion polls in recent weeks, is a vote to support nurses, rebuild social care and reward key workers.
He will say the choice on 6 May is a stronger, more secure and prosperous recovery out of the pandemic under Labour or the Tories cutting nurses' pay and NHS spending and raising taxes on families.
The super-poll this May, in which voters will be asked to take their own pens and pencils to polling stations, is bigger than normal because many of the elections are those postponed from last year because of coronavirus.
The elections taking place on 6 May include:
• Scottish Parliament
• Welsh Senedd
• Mayor of London and Greater London Assembly (postponed from 2020)
• Metro-mayor elections for the combined authorities of Cambridgeshire and Peterborough, West of England, West Yorkshire, Liverpool City Region, Greater Manchester, Tees Valley and the West Midlands (the last four postponed from 2020)
• 40 police and crime commissioners in England and Wales (postponed from 2020)
• Local authority mayors in Doncaster, North Tyneside, Bristol, Salford and Liverpool (the last three postponed from 2020)
• 24 county councils in England
• 127 English unitary, district and borough council elections (118 postponed from 2020)
The elections for the Scottish Parliament are particularly critical because Nicola Sturgeon will claim that an overall majority for the Scottish National Party will give her a mandate for a second independence referendum.
Besides Sir Keir, Labour's virtual campaign launch will include speeches by his deputy Angela Rayner, London mayor Sadiq Khan, Welsh First Minister Mark Drakeford, new Scottish leader Anas Sarwar and West Yorkshire metro-mayor candidate Tracy Brabin.
Turning up the heat on Boris Johnson and the Tories on NHS pay, Sir Keir will say: "My mum was a nurse, my sister was a nurse, my wife works for the NHS.
"I know how tough this year has been for our NHS and I know that now, more than ever, is the time to give our key workers a proper pay rise.
"Every vote in this election is a chance to show the Conservatives the British people value our NHS and our key workers so much more than this government does."
Attacking the Conservatives, Sir Keir will step up an attack he used against Mr Johnson at Prime Minister's Questions this week and claim the Tories are out of touch and out of ideas.
"A party that gives a 40% pay rise to Dominic Cummings, but a pay cut for our nurses," he will claim. "A party that gives billions to Serco, but nothing for our NHS.
"A party that spent a decade weakening the foundations of our economy - and now has no answer for the future. Only more of the same."
On Scotland, where Labour is attempting to fight back from third place behind the SNP and the Conservatives, Sir Keir will deride Ms Sturgeon's feud with Alex Salmond and attack her plans for a second referendum.
"After everything we've been through in the last year, the last thing we need now is more division," he will say .
"Yet, in Scotland, the SNP have shown they're too busy fighting among themselves to fight for the Scottish people. Their 13 years in power has seen child poverty rise and educational standards fall.
"Scotland now has the lowest life expectancy in Western Europe and the highest number of drug deaths. It's a record of shame and yet the SNP's only priority is another divisive referendum."
Sir Keir will also defend Labour's record in government in Wales, which will come under fierce attack from the Conservatives during the elections for the Senedd.
"In Wales, it's been Mark Drakeford's Labour government that's taken the tough decisions that were needed in the last year and now has a plan to take Wales forward," Sir Keir will claim.
"Mark's shown the leadership that's been sorely lacking in Westminster - and the difference that Labour in government can make.
"This election is the chance now to give Welsh Labour the tools to finish the job and to deliver a recovery that puts jobs and the NHS first."
Responding to Labour's campaign launch, Tory co-chairman Amanda Milling said: "Up and down the country Labour are failing to deliver locally.
"Labour politicians are distracted from delivering on your priorities and more interested in playing political games than delivering good services.
"Only the Conservatives can be trusted to focus on your priorities with a proven record of keeping bills down and providing better local services."