The healthcare watchdog has found further evidence of institutional abuse at the Áras Attracta care home.
The institution has until February to improve standards or it may be closed.
A three-year improvement plan was put in place for Áras Attracta in 2015 after a Prime Time programme unearthed disturbing and abusive practices in the centre.
Since then, HIQA inspectors have found little sustained improvement at the centre.
They have found evidence of institutional abuse, where residents were regularly harmed and injured through altercations with their peers.
They also found allegations of abuse were not properly handled.
In a statement, HIQA explained: "While there have been some improvements for a minority of residents, there is insufficient evidence to show that these improvements have been maintained."
Inspectors reported that staff said they do not have proper time to ensure residents social care needs are met.
As a result, many residents are spending significant amounts of time on their own with no social interaction - and where residents had plans for trips outside the home cancelled because of staffing issues.
Management at Áras Attracta were also found to be making decisions about residents' personal finances without consulting them
In September the Health Service Executive (HSE) was informed of the proposal to close Áras Attracta. A plan was then submitted to improve conditions for residents.
They have been given until February to improve the situation, or Áras Attracta may be closed.
The HSE says it welcomes the overview by HIQA.
It says: "In particular, the report acknowledges that while progress has been made at Áras Attracta, that staff are caring and respectful in their roles, and that the general health and well-being of residents is being met, full compliance in respect of a number of areas needs to be further addressed and on which the HSE is taking decisive action.
"These areas are being treated as a priority by the chief officer and his team in Community Health Organisation 2 (Galway, Mayo, Roscommon) with an emphasis on sustaining the progress already made and advancing it further.
"HIQA has made very valid findings in its report.
"Central to resolving the issues identified, including safeguarding, is to progress as rapidly as possible the de-congregation programme for Áras Attracta."
It says progress has been slowed "by challenges in the housing market in identifying, acquiring, and converting suitable accommodation in the community.
"While we don’t expect the housing boom to ease off in the foreseeable future, in order to overcome these challenges, we are continuing with our programme of sourcing suitable accommodation through our own estates management unit and through commissioning a number of specialised housing providers.
"While we have taken many steps to improve safeguarding, the single most significant thing we can do to address the concerns raised by HIQA in this area is to accelerate the process of de-congregation."
It adds that by the end of 2017, it is anticipated 16 people will have moved to their own homes in the community - and preparation is "well advanced" to facilitate a further 20 residents to move in 2018.
Additional reporting: Jack Quann