A report by the childcare inspectorate the Care Commission has found many facilities were "unsatisfactory" or "weak" in at least one area of their service in recent inspections, with many failing to meet standards across the board.
Of 658 premises inspected last year, a total of 84 were below par on at least one area including quality of care, environment, staffing or management. Common problems included lack of child protection training, "bored" children with few toys and games and limited access to outdoor play, staff failing to give children enough drinks and dirty or unhygienic premises.
Almost half of Scottish families pay for some form of childcare regularly, including nurseries, playgroups, crches and after-school clubs, with many providing an essential service for thousands of working parents.
Parents pay around 150 a week per child for a full-time place at a private nursery. After-school clubs cost between 15 and 50 a week.
But last night critics warned that "cheap labour" from young underqualified staff and a lack of Government funding meant many premises were falling below par.
The Care Commission, which inspects childcare facilities, introduced a new system last year which awards grades to allow parents the chance to judge performance easily: 1 is unsatisfactory, 2 weak, 3 adequate, 4 good, 5 very good and 6 excellent.
Most were judged adequate, good or very good, with 101 scoring very good and excellent in all areas. But a total of 24 were judged below par in all aspects they were inspected on, scoring unsatisfactory and weak across the board.
They included Primary Out of School Care Ltd, Paisley, which was criticised for "inconsistent" child protection training and for failing to have a working fire exit. Inspectors found the cleaning of toys was not acceptable.
Children complained they were "bored" and had a lack of games, and inspectors found they were not motivated by the club's activities.
The Carousel Nursery in Glasgow was found to have children in a room that was too hot, with a temperature of 27C, in July.
Another nursery, the Kilgour Kindergarten in Glasgow, was criticised for failing to provide children with drinks and a lack of staff training in child protection, infection control and food hygiene.
A supermarket crche, Dweezil's Adventure Centre, which operates from a branch of Asda in Aberdeen, scored poorly because of concerns about the fact children were within earshot of "inappropriate language" from members of the public and close to an area where store detectives apprehend shoplifters.
And Childcare in the Community at Whitehill Neighbourhood Centre in Hamilton was criticised for toilets which were "not fresh and clean" and a lack of staff numbers in the nursery.
These problems were reported in January 2008, but last week the centre was being re-inspected and may be regraded as a result.
Ronnie Hill, director of children's services regulation for the Care Commission, last night warned that services which fail to make improvements faced legal action.
He said: "Early findings suggest the quality of care on the whole is good or satisfactory. In some cases it is very good indeed.
"Where poor services do not improve sufficiently in an appropriate period of time, we will consider taking formal legal enforcement action to make sure that they do."
Ken Macintosh, Labour's spokesman for schools, described the revelations as "worrying". He said: "I am pleased the Care Commission have highlighted problems, but worried about the extent of them.
"A lot of childcare is provided by young, teenage girls and it's cheap labour. We need to address that by providing training."
Bronwen Cohen, chief executive of Children in Scotland, said: "It is very difficult for services which depend upon fees to develop in the way they should. The Government should put greater focus on funding services."
Siobhan Freegard, founder of the internet parents' group Netmums, said the checks were vital for many parents. She said: "Often parents don't have a choice because that's the only nursery or childcare facility in the area, and that's where these tests become really important. Any safety issue is something that has to be addressed immediately."
Last night childcare providers defended their facilities and said they had made improvements which will result in higher grades.
Whitehill and Kilgour Kindergarten said their services had made improvements which are expected to be reflected in forthcoming reports.
Primary Out of School Care Ltd in Paisley was re-inspected last month, and its grades increased so that all standards were adequate except for the quality of environment, which went from "unsatisfactory" to "weak".
A spokeswoman for Dweezil's said parents were "delighted" with the service and pointed out the Care Commission do not allow for the difference between crches, which provide a drop-off facility, and nurseries when they are doing inspections.
The Carousel Nursery did not comment.