The scrapping of start-date protections under Universal Credit is 'deeply alarming', the DWP has been told.
MSPs have warned thousands of Scots are suffering financially because UC no longer automatically backdates claims from when someone started their application.
Under previous rules, benefits would be calculated from the date an application began but with UC the start date is only protected if a claimant turns up in person to a job centre when they apply.
Bob Doris, convener of the Social Security Committee in Holyrood has now written to Work and Pensions Secretary Amber Rudd about 'the retrograde step for claimants' and demanded an urgent review of the change.
In his letter, Doris said: "As I am sure you know, there can be many reasons why someone may not be in a position to submit a completed claim on the first day of entitlement.
"It may not be possible to get to a job centre, particularly given recent closures."
He added: "There is no doubt this is a backward step and this ill-thought-out change will unfairly impact the most vulnerable people in Scottish society.
"At a recent committee meeting, we heard from Glasgow City Council that each and every month 200 claimants, from Glasgow alone, will suffer financially due to the council no longer being able to protect the date of claim.
"This is deeply concerning when you consider the number of claimants that would be affected across Scotland.
"There is already a minimum wait of five weeks for those submitting a claim to receive financial support so this new development is simply not acceptable.
"Whether the DWP were aware of the impact this change would have or not, we want to see it swiftly resolved."
