The new Universal Credit benefits system is a "bad joke" which will lead to thousands of sick and disabled people losing out on help, MSPs have been told.
Universal Credit replaces six benefits - income support, jobseeker's allowance, employment support allowance, housing benefit, child tax credit and working tax credit - with a single payment and is being rolled out across the UK.
It is aimed at simplifying benefits but experts told the Scottish Parliament's Social Security Committee on Thursday it has made claiming more complex and is putting people in debt - leading them to fall behind on council tax and rent and having to attend food banks - and does not make work pay.
The committee heard that Citizens Advice staff "can't cope" with the changes and "people are falling through the gap".
Archie Campbell, benefits representative at Musselburgh Citizens Advice Bureau which is one of three areas in Scotland running the full scheme, said: "One of the policy statements was 'simplifying the benefits system and making work pay'. Now, I've noticed they've taken that down from their website because, quite frankly, it's a bad joke.
"The benefits system is very complex now. We've got trouble with our advisers at Citizens Advice. They just can't cope with all the changes.
"Generally speaking, apart from people who wouldn't have been eligible for working tax credit because of the hours they worked, it doesn't make work pay as much as the previous system."
He said those people would be winners in the "universal credit lottery" but "for every other group I just see it as a way of getting into debt" as payments are not made for six weeks and a single wage payment putting claimants over the threshold means they have to apply again.
He added: "It's just not been thought through at all. I think this is incompetence rather than being down to something that is being done on purpose."
He said some sick and disabled people moving from the old system were missing out on premium payments of £62 a week and legislation to rectify that has been delayed to 2019.
He said: "You're going to get thousands upon thousands of claimants claiming disability benefits and sickness benefits who are going to lose out substantially."
Mr Campbell also criticised the IT system, saying it is "so badly designed" that "even people who are IT literate and highly intelligent" miss a crucial link telling them to phone to complete their claim.
Rob Gowans, policy officer at Citizens Advice Scotland, said the digital-first system meant claimants struggle as a recent CAS survey showed 59% could not make a benefits claim without help.
Advocacy worker Kyna Reeves said "to get a claim off the ground is much harder for people now" due to time limits and requirements such as a bank account, email address and doctor's note.
She said: "People do fall through the gap. Some of the most vulnerable people we've worked with have to start the claim again because it lapses after seven days."