The Joseph Rowntree Foundation's (JRF) Poverty in Scotland 2021 report warns immediate steps are needed for the Scottish Government to avoid missing its own targets on child poverty by 2024.
It recommends immediately doubling the current Scottish Child Payment to £20 per week for every eligible child under six years old.
The planned cut to the £20-per-week Universal Credit boost from Wednesday "makes the task more urgent", said the JRF.
Some 450,000 families in Scotland will be £1,040 poorer per year as a result of the cut, it added.
Figures in the report, "which paints a picture of poverty levels in Scotland just before the Covid-19 pandemic", said around a million people, including a quarter of a million children, were trapped in poverty.
It said there have been failures to tackle high levels of deprivation among key priority groups which include: ethnic minority families, families where someone is disabled, those with a child younger than one, and single-parent households.
More than eight in 10 children in poverty are in one of these groups.
Some 100,000 impoverished children live in a household where someone is disabled - 40% of all children in poverty in Scotland, the report highlighted.
It said: "It is time for the Scottish Government to stop walking and start running, by immediately doubling the Scottish Child Payment."
Despite making up just 7 per cent of the population, children from minority ethnic backgrounds count for 16 per cent of all children in poverty, it added.
It said: "Much evidence has highlighted the unequal impact the pandemic has had on many of these groups, meaning their current situations could be much worse."
By April 2024 the Scottish Government hopes to have reduced relative child poverty to below 18 per cent.
The report concluded: "We will miss that target, and by some way, unless urgent action, at scale, is taken now."
By doubling the Scottish Child Payment as quickly as possible, the child poverty rate would drop to 22 per cent by April 2024, still four percentage points short of the interim targets, it adds.
Chris Birt, associate director of the JRF in Scotland said: "The Scottish Government has rightly set a national mission to end child poverty and has put in place steps to move us in the right direction.
"But we are on course to miss our targets by some distance. Such a political failure would have a profound human cost - tens of thousands more children will experience childhoods blighted by hardship and anxiety.
"It is time for the Scottish Government to stop walking and start running, by immediately doubling the Scottish Child Payment and by significantly increasing the scale and pace of its programme to support families in priority groups.
"The responsibility for the cut to Universal Credit falls squarely at the UK Government's door. It is a failure of both compassion and of policy."
Figures from National Records of Scotland from 2021 show people in the most deprived communities are 18 times more likely to die a drug-related death, more than four times more likely to die from alcohol, while the rates of suicide are three times higher than the most affluent areas, the report said.
The report was produced alongside the End Poverty Scotland Group, an advisory group of people from across Scotland with first-hand experience of living on a low income.