More than 4,500 children attending pre-schools and creches have been exposed to staff who were not garda vetted.
Some 106 centres inspected last year failed to carry out garda checks on all staff who were working directly with children under the age of six.
The serious protection failures are exposed in the annual Early Years Inspectorate report from Tusla.
It also revealed that 51 services, with 2,400 children, had no records on fire maintenance, in line with safety regulations.
Tusla said an analysis of 288 inspection reports showed more centres were now complying with the rules.
However, Tanya Ward, of the Children's Rights Alliance, warned that while over three- quarters were meeting minimum standards, one in five were still breaching safety.
"Young children are vulnerable," she said.
"The inspections provide us with evidence of the continued need for national regulation and inspection to keep children safe and well."
The analysis revealed:
- Sixty-three services did not meet basic health, welfare and development needs. These cared for 2,700 children.
- A serious safety risk was identified where window blind cords were hanging loosely and could be accessed by children, creating a danger that they could be a victim of strangulation. Around 500 youngsters in 18 childcare centres were exposed to this potentially lethal hazard.
- Trailing flexes and trip hazards owing to unsafe flooring were found.
- A full water tank with a loose top was discovered in an outdoor area which could have put a child at risk of drowning if they had climbed up and fallen in.
- Lack of supervision also emerged as an issue, with children at the top of the slide in the outdoor area while two adults were involved in hand-painting.
- A swing in an outdoor area was not properly supervised at all times and an incident was observed where a child on the apparatus knocked over another.
- Another centre had an external door which was not secured to prevent somebody unauthorised coming in.
- A gate at the side of an outdoor play area did not prevent unauthorised access.
- In another centre children's hands were not washed before snack time and only occasionally after using the toilet.
- lIn one service the first aid boxes were not suitably equipped and many of the items were out of date.
- lA swing bin lid was used for dirty nappies, into which children were putting their hands.
- However, Tusla said 2016 also marked developments.
The child and family agency held a series of nationwide seminars on regulatory changes during the year which were attended by 3,800 early years providers.
Tusla's director of quality assurance, Brian Lee, said: "I'm delighted to see that Tusla's Early Years Inspectorate carried out over 2,008 inspections in 2016, which resulted in positive changes and improvements in key areas such as the health, welfare and development of children, safety of services, governance and facilities."
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