Plans to give every Scot a basic income of £100 a week would risk making child poverty worse, according to a thinktank.

Four councils have won £250,000 from the Scottish Government to test the idea of a Universal Basic Income (UBI) for every citizen, to reduce inequality and simplify or replace the complex benefits system.

However the Institute for Public Policy and Research has warned that a Scotland-wide scheme could cost £20bn per year, and increase relative child poverty by up to 35,000.

The Institute said by increasing the median income, a so-called Citizen's Income would raise the relative poverty line, leaving more families with children below the line.

Assuming a UBI was set at just over £100 per week per adult and £50 per week per child, even in the best case scenario - measuring poverty in Scotland by comparison with incomes in England - only 60,000 children would be lifted out of poverty, the IPPR said.

It has been estimated that around 230,000 children, almost one in four, are living in poverty.

A spokeswoman for the IPPR said poverty was increasing faster than a UBI would be able to take people out of poverty, and would get rid of means-tested benefits, by replacing money targeted at the poorest with universal payments.

She claimed topping up the child element of Universal Credit by £150 per month could lift 100,000 children out of relative poverty in Scotland, at a much lower cost of £950m per year.

Russell Gunson, Director of IPPR Scotland, said: “The idea of a Universal Basic Income has gained attention in recent years in Scotland with supporters across the political spectrum. And it’s good to research the idea and test its feasibility. However, our modelling shows that far from being an anti-poverty measure, a UBI could increase relative child poverty in Scotland.

"There may be a number of good reasons to consider the introduction of a Universal Basic Income in Scotland but it seems reducing relative child poverty is not one of them.

“A UBI could cost an eye-watering amount of money, around £20bn per year in Scotland at these rates. Even just a small proportion of that could be used to make huge inroads into poverty rates in Scotland.”

However the Scottish Greens, who have backed the policy, said the Institute's analysis was simplistic and misleading, by looking at the policy in isolation.

The party's co-convener Patrick Harvie said: "Greens have always put forward the policy in conjunction with a host of other actions." These include the 'real' living wage, creating better jobs in new industries, ending benefit sanctions for those attending work programmes and rebalancing of the tax system in favour of lower earners, he said. "Seen again these wider progressive policies, a Basic Income would help to protect people against exploitative low pay, provide stability for people in precarious work, and enable people to strike their own balance between paid work, caring, education and other commitments."

A spokesman for Reform Scotland, who have also proposed a form of UBI, said: “Our analysis of two years ago made absolutely clear that the introduction of a basic income guarantee would come at a significant cost to the taxpayer, but that it would deliver significant new benefits, including improving incentives to work.

"The basic income payment we advocate would be paid in addition to other benefits including housing benefit, many of which have since been folded into the universal credit system, and we therefore are surprised at any unexplained links to child poverty levels.”