The First Minister was furiously criticised by Scottish Liberal Democrat leader Willie Rennie, who said that five years into a free childcare policy, only a third of eligible families were taking up places - less than half the rate in England.
Shouting in the Holyrood chamber at First Minister's Questions, Mr Rennie said: "You can't match the Tories Nicola, how embarrassing is that?"
And as the First Minister outlined her government's actions on childcare, he shouted: "Shocking, complacent".
Mr Rennie had raised a report by Save the Children which expressed concern that thousands of young children living in poverty are missing out on “the significant benefits that early learning and childcare can provide”. The charity also warned that the “lack of progress in this area will jeopardise the Scottish Government’s overarching ambition to close the poverty-related attainment gap”.
Mr Rennie said: “In 2014, after months of refusal, Alex Salmond eventually agreed to introduce free nursery education for all two-year-olds in poverty. Five years later, only one third of those children are getting this foundation. Why is this First Minister failing these children?"
Ms Sturgeon said she did not accept Mr Rennie's premise. "There is availability for childcare across Scotland for vulnerable two-year-olds, in addition to the provision for three and four-year-olds, and we continue to encourage parents who want to make use of that to do so.
"Our job is to make sure that provision is there, and we are working with local authorities and investing significant sums of money into local authorities to transform childcare to double the provision that's currently available by the end of this parliament. This is one of the big success stories of this parliament and it's one we should be proud of and continue to work to build upon."
But Mr Rennie said: “Save the Children are not impressed. In page after page of evidence they show that children are missing out and that this could jeopardise closing the poverty-related attainment gap. It’s meant to be the First Minister’s top priority but it was evident today that she doesn’t know just how far behind this critical policy is.
"In England, over 70 per cent of two-year-olds in poverty are receiving free nursery education. That’s double the rate in Scotland. It's unbelievable the Conservative government is able to reach more children in poverty than the SNP. It's been five years. Does the FM not think he should have made more progress by now?"
Ms Sturgeon hit back saying that Mr Rennie was in "his usual role of defending a Conservative government - prompting his outburst.
She added: "This government is doing significantly more in expanding early years and childcare than the government south of the border and that will continue to be the case."