One in five people are spending more than 40% of their net income on rent.
A survey by NABCO - Ireland's co-operative housing provider - shows 23% of all tenants are afraid of losing their accommodation, but this climbs to 38% in Dublin.
The figures are worst for those with incomes of less that €20k where 45% of people are afraid of losing their home.
Nearly one third of the 1,000 respondents, 32%, did not know if they had any formal lease and only 7% identified themselves as having one. It also found that a third of tenants feel that they don’t know their rights and four in 10 don’t know where to look for help.
CEO of NABCO Kieran Brennan says that figure is worrying.
Mr Brennan said: "Under the legislation, after six months you acquire certain rights anyway, but it is worrying that as many as one in three wouldn't have that (formal lease).
"Also, despite the good work of people like Threshold and the PRTB, 41% of tenants said they were not aware of where to get information about their tenant rights."
The survey went on to show that 42% of Dubliners have seen their rent increase in the last 18 months, while in the rest of the country, 19% have had this experience.
Up to 67% of Dubliners expect their rent to increase in the next 18 months, with 29% of people in the rest of Ireland expect their rent to go up.
Mr Brennan said: "The figures in the survey also show major pent up housing demand. More than 1 in 10 households where someone would like to move out but can’t.
"The high price of accommodation and a shortage of properties are identified as the main barriers to people starting their own households. Nine in 10 people agree that the Central Bank proposals (that most new mortgages would require loan to value ratios of 80% or less) are going to make this situation worse.
"This research provides a compelling case for greatly increasing the supply of housing in every segment of the housing market in the Dublin region especially."
