The Scottish government is at risk of missing its own child poverty targets by more than 100,000 children, according to projections from the Resolution Foundation.

Westminster austerity measures will put child poverty across the country on course to hit a 20-year peak of about 29% of children living in relative poverty by 2023, its report forecasts. The figure is considerably higher than the Scottish government’s target of 18%.

The most recent figures on relative child poverty show 23% of children across Scotland were living on less than 60% of median household incomes in 2016-17.

In November 2017, the Holyrood parliament passed Scotland’s first child poverty bill, which reintroduced the statutory targets abolished by the UK government a year earlier.

Adam Corlett, senior economic analyst at the Resolution Foundation, acknowledged that the rise in child poverty “is almost entirely driven by UK-wide decisions”, including the four-year freeze on working-age benefits and the two-child limit on working-age benefit support.

But Corlett added: “But that doesn’t mean policymakers in Scotland are powerless to respond. If the Scottish government is to meet its ambitious – and welcome – child poverty reduction targets, it will need to implement much more radical changes to social security than it has done to date.”

The Scottish government was heavily criticised last month after it announced the full devolution of the welfare benefits, instituted after the 2014 independence referendum, was to be delayed until 2024, despite pledging it would be completed by the end of this parliamentary term.

While the projection does not include new Scottish government policies such as the Best Start Grant, the (Disability-related) Carers’ Allowance Supplement and more generous council tax support, the report argues that these policies are dwarfed in scale by ongoing impact of the former UK chancellor George Osborne’s 2015 budget.

Campaigners have also raised concerns that the Scottish government’s proposed income supplement, specifically intended to reduce child poverty, remains ill-defined and uncosted, and will not be implemented in time to mitigate the devastating effects of Westminster austerity.

John Dickie, of Child Poverty Action Group Scotland, said: “We have huge concerns that the 2022 timetable for a new income supplement fails to reflect the extraordinary increase in child poverty that the country faces. A £5 top-up to child benefit implemented now could, for example, lift thousands of children out of poverty and protect many more from hardship.”

Holyrood’s communities secretary Aileen Campbell insisted that the Scottish government is doing “all we can with the powers we have to mitigate those cuts, protect people on low incomes, and secure our ambitions to eradicate child poverty,” including using the new social security powers.

Campbell said: “This report is a stark reminder of the challenges we face to end child poverty in Scotland. We are tackling child poverty with one hand behind our back in the face of the devastating impact of the UK government’s welfare cuts and benefits freeze which are set to push thousands more of the poorest and most vulnerable families into poverty.”