MSPs have called on the UK Work and Pensions secretary to fix “shocking” problems with Universal Credit before it is extended in Scotland, claiming it is driving people to “breaking point”.

The single payment replaces six benefits – income support, jobseeker’s allowance, employment support allowance, housing benefit, child tax credit and working tax credit – and is paid to claimants directly.

Universal Credit has been introduced in pilot areas in Scotland ahead of a planned roll-out and now Holyrood’s Social Security Committee has written to Work and Pensions Secretary Damian Green urging him to address “fundamental, systemic issues” with the payment before it is expanded.

The committee met with administrative staff and claimants in the Musselburgh pilot area and heard about unacceptable delays of eight or nine weeks in being paid benefits, pushing people into rent arrears.

Committee members also heard local jobcentres are ill-equipped to support claimants effectively. The letter calls for the Universal Credit helpline to be free, as claimants are charged currently and can face long call times.

Universal Credit was aimed at simplifying the benefits system and making work pay but the letter states: “Our evidence tells us in practice people find the system far from simplified, eligibility is unclear and it is more difficult than before to even initiate a claim.”

Committee convener Sandra White said: “The whole purpose of Universal Credit was to simplify the process of claiming for social security by rolling six benefits into the one payment.

“We heard some shocking stories of people who are being driven to breaking point because this system simply doesn’t work for them.

“We recognise any new system is always going to have some issues but most of the committee agree that if these fundamental, systemic issues are not addressed then Universal Credit is not a workable system.

“Even more concerning is that some of the problems are likely to be made worse by the closure of jobcentres, with more pressure being put on the third sector to help some of our most vulnerable people in Scotland.”