A coalition of church leaders, children’s charities, anti-poverty groups and senior academics have urged Finance Secretary Derek Mackay to increase child benefit by £5 a week in his Budget this week.

The experts issued their demand days after a new report revealed that nearly a quarter of a million children north of the border are in poverty.

Scottish Labour leader Richard Leonard backed the call: "Children living in poverty cannot wait several years for these additional funds - they need them now."

Following the independence referendum, the cross-party Smith Commission led to Holyrood acquiring new powers over taxation and social security.

Among the basket of powers given to MSPs was the ability to create new benefits and top-up existing programmes reserved to Westminster.

The SNP Government has since confirmed it will introduce an income supplement by 2022, although Ministers have yet to decide on what form it will take.

According to the Joseph Rowntree Foundation, around one million Scots are in poverty, of which 230,000 are children.

In two separate letters, a range of senior figures have called on the Government to bring forward their top-up plan by announcing an income boost in Wednesday’s Budget.

Their preferred option is to increase child benefit, which is currently set at £20.70 a week for the first child, by £5, in line with the high-profile ‘Give Me Five’ campaign.

In their letter to Mackay, four senior church figures - Church of Scotland Moderator Rt Rev Susan Brown, The Most Rev Mark Strange of the Scottish Episcopal Church, Joan Cook of the Scottish Unitarian Association, and Bishop William Nolan - wrote:

“There is a compelling argument to act with greater urgency in implementing the income supplement. Given the levels of poverty that currently exist in Scotland, we urge you to consider using the budget to deliver the income supplement in the next year, rather than by the current timescale of 2022.

“Doing so would reflect the great need that families across Scotland must be lifted out of poverty right now, rather than in several years’ time."

They added: “As supporters of the Give Me Five campaign, we ask that – as well as bringing forward the delivery of the supplement – you also consider doing so via topping up child benefit, which would immediately lift tens of thousands of children out of poverty.”

In the second letter to the Finance Secretary, over twenty prominent individuals called for child benefit to be increased.

These include Satwat Rehman at One Parent Families Scotland, Children 1st Chief Executive Mary Glasgow, Scottish Drugs Forum CEO David Liddell, STUC General Secretary Grahame Smith, Poverty Alliance Director Peter Kelly and Child Poverty Action Group in Scotland Director John Dickie.

It also included senior figures in Cranhill Development Trust, children’s charity Aberlour, Justice and Peace Scotland, Energy Action Scotland, Close the Gap and Engender.

They wrote: “As a non-means tested entitlement, it [child benefit] has a high take-up rate and is less expensive to administer, and we continue to believe that topping up child benefit would represent a most effective and impactful way of delivering the new income supplement.

The signatories also stated that they are “seriously concerned” that the 2022 timescale for an income top up is “not reflective of the urgency with which it is required”.

Dickie said: “These letters demonstrate the extraordinary breadth and depth of support across Scotland for an immediate boost to family incomes to help tackle the devastating hardship too many children are facing.

“Along with faith groups, trade unions and children's charities we urge the Finance Secretary to prioritise financial support for families as a matter of urgency. A £5 top up to child benefit would be one way of lifting thousands of children out of poverty and protecting many more from the damage poverty wreaks.”

The SNP has so far resisted the policy on the grounds that the payment would benefit families not in poverty.

SNP Communities Secretary Aileen Campbell said: “Scotland is the only part of the UK to have ambitious targets to reduce, and ultimately eradicate, child poverty. We are developing a new income supplement to provide additional financial support to families who need it most as research shows that topping up Child Benefit, which remains reserved to the UK Government, is not the most efficient or effective way to lift children out of poverty, nor would it be quick or simple.

However, the Government is facing political pressure to back the £5 a week increase, as the Greens and Scottish Labour are in favour of the move.

Leonard said: "This is a hugely significant intervention in the budget debate by faith leaders, charities, anti-poverty campaigns and the STUC uniting to call for Scotland's powers to be used in the interests of the many, not the few.

"Derek Mackay must listen to these church leaders, charities and Labour and raise Child Benefit by £5 per week in his budget on Wednesday.

"This would lift around 30,000 children out of poverty and help families across Scotland."

Scottish Greens MSP Alison Johnstone said: "Topping up Child Benefit was a Green manifesto proposal that would lift thousands of families out of poverty. While there's no doubt poverty has been exacerbated by the UK Government's harmful cuts, we can't just wring our hands when we have the power in Scotland to soften the blow."