In a joint letter from parliamentary committees in Westminster, the Northern Irish Assembly, the Welsh Senedd and the Scottish Parliament, convenors have urged chancellor Rishi Sunak and work and pensions secretary Therese Coffey to keep in place the uplift.

Signed by Labour’s Stephen Timms at Westminster, the SNP’s Neil Gray for Holyrood, Paula Bradley of the DUP for Stormont and Welsh Labour’s Jenny Rathbone at the Senedd in Cardiff, the joint letter from the four committee chairs of the UK’s four parliaments is thought to be a first.

In the letter, they say the £20 increase in the Universal Credit payments has been “a lifeline for millions of families, saving them from being impoverished”, adding that they hoped the UK Government would “take seriously our view that the uplift should be extended”.

The letter reads: “Ending the uplift would mean that the six million people claiming Universal Credit will lose £1,040 in annual income overnight.

“The Joseph Rowntree Foundation has estimated that removing the uplift would force 500,000 people, including 200,000 children, into poverty.

“Families on the lowest incomes, those with children and particularly single parents, BAME families, and families where someone is disabled are disproportionately affected.”

They warn the ministers: “You also risk removing this support from families at the very time unemployment is expected to peak, as the Coronavirus Job Retention Scheme comes to an end.”

Opposition politicians, union leaders and anti-poverty campaigners including the Scottish Federation of Housing Associations (SFHA) and Citizens Advice Scotland (CAS) have all been urging ministers to make the increase to the benefit payment permanent.

A government spokesperson said: “Universal Credit has provided a vital safety net for six million people during the pandemic, and we announced the temporary uplift as part of a £400bn package of measures put in place that will last well beyond the end of the roadmap.

“Our focus now is on our multi-billion pound Plan for Jobs, which will support people in the long-term by helping them learn new skills and increase their hours or find new work.”