SNP politicians backed children's minister Aileen Campbell by turning down two key votes to amend the Children and Young People Bill being scrutinised at Holyrood.
Labour wanted to push the SNP into voting now to enshrine a commitment to give 600 hours of childcare to the "most vulnerable" two-year-olds.
The proposal is in step with an announcement last week from First Minister Alex Salmond, who wants to meet that goal, representing 15% of two-year-olds, from August.
One year later, the Government wants to extend childcare further to 27% of all two-year-olds by widening entitlement to families who receive certain welfare benefits such as income support.
The SNP says that after independence it would provide 1,140 annual care hours, for one to four-year-olds, allowing more parents to return to work.
Labour MSP Neil Bibby said that by refusing to act now the SNP is showing a lack of commitment to its own childcare policies which could benefit 30,000 children, saving £2,000 a year for families.
"This would be real action to help with the cost of living and help take children out of poverty," he said.
"It is also identical to the first stage of the plans written in the White Paper from the Scottish Government."
He added: "There seems to be a real reluctance to putting additional entitlements for two-year-olds on the face of the Bill. The obvious question is why?"
Ms Campbell, appearing before the Education and Culture Committee, said the SNP's childcare proposals will build on the existing Bill.
Bigger change can only come with the powers of independence, she said.
"While we share Neil Bibby's ambitions, we have to be absolutely realistic - there are not the resources to do what he proposes," she told MSPs.
Stewart Maxwell, the SNP covener of the committee, said: "Without the proper analysis of where the finance is coming from, I find it impossible that any member should seriously consider supporting amendments in the name of Neil Bibby."
Using £300 million of money from the UK Government to Scotland shows a gobsmacking degree of financial illiteracy, he said. Some of that money is capital funds and some has to be paid back.
The children's minister also rejected an attempt to change the way free nursery care is provided.
SNP members voted against Conservative MSP Liz Smith's attempt to correct an "anomaly" which means only half of children born in 2011 and last year will be guaranteed two years of nursery provision.
She highlighted research by think-tank Reform Scotland which showed the current legal entitlement to Scottish Government-funded places can vary by up to 317 hours - or £1,033 - based on date of birth.
Reform Scotland's research, published in November, showed a child born between March 1 and August 31 will be entitled to two years' nursery provision before beginning school.
A child born between September 1 and December 31 gets 18 months and a child born between January 1 and February 28, assuming he or she attends school aged four, will get 15 months, according to the research.
Ms Smith said: "If there are to be arbitrary points of cut-off, that's fine. But surely we need to be sure that it treats all children equally and doesn't discriminate just because of their birthday date."
Ms Campbell said amending the Bill now is unnecessary and that changes can be made at a later date.
"This Bill represents the first step in our ongoing journey to transforming childcare, starting with those who need it most, and that's the most vulnerable two-year-olds," she said.
"Last week we indicated our intention to expand that further, so I don't support the amendments."
SNP member Colin Beattie said: "My concern with this is there seems to be no funding available for this at the moment. The amendment doesn't indicate where funds will come from."
The Government approach is "eminently sensible", he told the committee.