Kezia Dugdale MSP claimed independent experts had shown the flagship proposals to be “uncosted” and “ill-thought through”.
Labour will challenge the Scottish Government on its plans in an opposition debate at Holyrood today.
Ministers have previously argued that the powers of independence are needed to radically transform childcare provision in Scotland.
Under Scottish Government plans children could receive 1,140 hours of childcare a year after a Yes vote in September’s referendum, with supporters of the policy arguing this will allow many more parents to return to work.
A six per cent increase in the number of women in the labour market could boost tax revenues by as much as £700 million, according to the Government.
While ministers hope to generate an extra £2.2 billion for the economy by expanding free childcare, the Scottish Parliament Information Centre (Spice) has said there is “no evidence” their proposals would see more women return to work.
A £2.2 billion boost to the economy would require 104,000 women to join the workforce, but there are only 64,000 women who are currently economically inactive, Spice research claimed last month.
‘Cobbled together’ claim
Speaking ahead of today’s debate Ms Dugdale said: “We need a new approach to finding a way in which we can provide affordable quality childcare for all of Scotland’s families. That means that parties need to work together to find a solution. Families deserve nothing less. They certainly deserve more than what’s being cobbled together by the Scottish Government.
“The Scottish Government’s flagship childcare proposals have been shown by independent experts to be uncosted, ill-thought through and with no real consideration of how they will work.
“Writing policies on the back of a fag packet isn’t how we should be approaching serious government in Scotland. But the SNP are only interested in grabbing headlines with their announcements. If they were serious about this policy, it would have been worked out, properly considered, with clear costings and analysis.”
A Scottish Government spokesman said: “More than a quarter of a billion pounds is being invested over the next two years to expand funded early learning and childcare for three and four-year-olds from 475 to 600 hours from August and extending this entitlement to the most vulnerable 27 per cent of two-year-olds over two years.
“We have clearly stated that we will build on this steadily and sustainably, with a further investment of £3.5 million going into developing the workforce to meet the growing demand.
“This transformation in childcare has been recognised by charities, unions, industry groups and others as having the potential to give families greater support to pursue careers and improve their children’s care that will benefit the whole country.”