The campaign group, Fair Funding for Our Kids, is demanding Glasgow City Council rethinks its strategy when it comes to buying places for youngsters in private nurseries.
Parents also say the local authority is breaking the law by not providing them with five free sessions a week, which applies to children over the age of three.
They are frustrated that many private nurseries in Glasgow have had their funding removed, and say there are not enough spaces in council-run facilities.
Initially started by parents from Clarence House nursery in Maryhill, the group has joined forces with others from across the city who are also in the same situation.
Seonaid Daly, from Finnieston, whose daughter goes to a Yorkhill nursery, said the options for working parents were "limited" as few council nurseries run out with term time or for full days.
The 32-year-old said: "The few that do offer this service still seem to prioritise parents seeking part time places and those who have social needs.
"Working parents are de-prioritised. They simply aren't providing enough places or a suitable service for children with working parents or carers.
"It is their legal obligation to provide my child with five sessions, they haven't offered me anything yet and they are doing that right across the board."
MSP Sandra White, who looks after the Kelvin Ward, has stepped in to help the campaigners and vowed to contact Education Minister Michael Russell MSP.
A council spokeswoman said there had been no reduction in the number of places, and said the local authority had even over-purchased places in the city centre.
She said: "We have in fact increased the number as well as funding per place by 26% with the new contracts. Our early years officers will continue to review the situation across the city and work with families to find solution."