Labour leader Sir Keir Starmer is to make his first visit to Wales since winning the party leadership.
He will visit an aerospace research and manufacturing facility in Flintshire, following July’s announcement of major job losses at Airbus in Broughton.
Before Thursday’s visit, he said UK ministers should reverse plans to end the furlough scheme to save Welsh jobs.
The Treasury said it had given Labour Welsh ministers money to “plan their own support schemes”.
Sir Keir wants a reformed furlough programme to support sectors of the economy that have been worst-hit by coronavirus.
The job retention, or furlough scheme, was introduced by the UK Treasury at the beginning of the pandemic to prevent mass redundancies and was originally intended to last until the end of July.
Since the start of August, employers must pay National Insurance and pension contributions, then 10% of pay from September, rising to 20% in October.
The entire scheme is due to finish at the end of October.
A total of 1,435 jobs are being cut at Airbus’s Broughton wing factory, as part of plans to axe 15,000 jobs worldwide in response to the hit it has taken during the pandemic.
“The UK government’s blanket withdrawal of the furlough scheme is a historic mistake which threatens Welsh jobs,” Sir Keir said.
“The devastating job losses announced at Airbus show how high the stakes are.
“The Welsh Government has done a huge amount to support struggling businesses, but the action needed on the furlough scheme can only come from Westminster,” he added, calling on Welsh Conservative MPs and Senedd members to join Labour’s campaign to force UK ministers to change their stance.
A UK Treasury spokesperson said: “The furlough scheme was unprecedented and has so far supported the wages of over 378,000 people in Wales and will run for eight months in total.
“We have also recently announced our £1,000 job retention bonus to ensure we protect as many jobs as possible.
“We continue to support closed sectors through our targeted package of support that includes tax deferrals and VAT cuts, rent moratoriums and loans and we will continue to work closely with them during this difficult time.
“The Welsh Government has also been guaranteed at least £4bn this year, on top of the funding announced at the Spring Budget, giving them the certainty they need to plan their own support schemes over the next few months.”
Sir Keir took over the Labour leadership from Jeremy Corbyn in April, in the aftermath of a general election in which the Conservatives took six Welsh seats from Labour, including Wrexham, Vale of Clwyd, Clwyd South and Delyn in north east Wales.
The losses left the party with only one seat in north Wales – Alyn and Deeside.
The new leader has held a series of virtual meetings with voters, including in north east Wales, as part of efforts to reconnect the party with traditional Labour voters it has lost.
His visit comes ahead of a Senedd election next May, in which the party will be seeking a sixth term in office.
Labour had led the Welsh Government continuously since devolution in 1999, including two spells with support from other political parties.