The Fair Deal scheme waiting list increased by 30% last month.
New figures seen by Fianna Fáil show in the two weeks up to the end of Septmber the number rose from 525 to 686.
The party's Older People spokesperson, Mary Butler, says she is deeply concerned by the "wild fluctuations" in the figure.
She says the problem will get worse over winter unless the government makes a serious effort to tackle it.
"In just two weeks the numbers waiting for placement under the Fair Deal scheme shot up by over 160," said Deputy Butler.
"This is an alarming escalation in a very short period of time, and points to serious issues within the system.
"I am fearful that this is a sign of things to come as Winter draws closer.
The Irish Nurses and Midwives Organisation (INMO) have already said that September was the worst month of 2019 for trolley figures and this will have a knock-on effect on Fair Deal placement.
“We also learned that by the middle of September there were 745 patients who had not been discharged from hospitals despite being deemed medically fit.
"They had nowhere to go as there were no supports in place for them.
“It’s a vicious cycle and will continue unless and until the Minister takes a system wide approach in fixing it.”