Families and carers say they have had no day service to attend or a significant reduction in services since March.
Protesters said people with disabilities are being left behind while the rest of the country is being reopened.
Linda Comerford, spokeswoman for campaign group Enough is Enough, said the Resumption Framework for Adult Disability Day Services is, at best, “vague, non-committal and offers no reassurance”.
For parents and families to witness this and see it continue, despite our best efforts to help our loved one, is gut-wrenching
“There is no indication or plan of when day services can fully reopen and the two-metre social distancing rule is drastically reducing centres’ capacity,” Ms Comerford said.
“The document also states that ‘the availability of safe transport is essential to the delivery of day services across the country’, yet many families are being told that there will be no transport available to them.
“Going from 30 hours a week to six, nine or 15 hours divided up into three hours a day, depending on the service and the needs of an individual, is a very inferior service. Where is the rest of an individual’s funding going?
“Zoom calls, activity packs to do at home or someone coming to an adult’s home to bring them for a walk cannot be deemed a service.”
She said families and carers are being forced to take on a much greater role but with no support or financial assistance.
We are not going to leave these people behind – we are currently leaving them behind. It is completely and utterly unacceptable
“Adults with disabilities are missing their friends, their routines and their support workers,” she added.
“Many are regressing, becoming withdrawn, having increased challenging or aggressive behaviour and feel lost.
“For parents and families to witness this and see it continue, despite our best efforts to help our loved one, is gut-wrenching.
“Time and time again the Government consistently fail those with disabilities and carers. It is simply not good enough and must change.”
Labour leader Alan Kelly said: “Can you imagine, in the middle of a pandemic, we have families of people with intellectual disabilities outside the Dáil protesting? Can you imagine any other group of people in this country during the Covid-19 crisis that have actually come to protest outside our national parliament?
“I have raised this for the past three weeks in a row. We are not going to leave these people behind – we are currently leaving them behind. It is completely and utterly unacceptable.
“We live in a republic, we must treat everyone as equals. We need to ensure that our most vulnerable in this crisis are taken care of.”