Labour would reimpose a requirement on local councils to provide childcare via Sure Start centres in a bid to "save" the network and ease chronic shortages of places , shadow education secretary Tristram Hunt announced.
The network of facilities for parents in mostly deprived areas is cherished by the party as one of the most significant initiatives of its last spell in power.
But it says the removal of the statutory obligation by the coalition Government has directly led to a dramatic decline in numbers - with 720 fewer now than in 2010 and many more mothballed or running much-reduced hours.
With half of authorities predicting budget cuts will further restrict the service in the next two years, Mr Hunt said it was vital to restore the pressure to "put the lights back on, get the kids back in".
The Opposition said it would make it easier for cash-strapped town halls to find and engage outside providers, by matching them up with childcare firms and charities "desperate" to find suitable and affordable premises and by reducing red tape.
Analysis by the 4Children charity suggested the move could double the places provided through Sure Start to 118,000, the party said.
"It is a scandal that these brilliant community assets are being mothballed or even closed at a time when parents are crying out for decent childcare in their communities," Mr Hunt said.
"We will not succeed as country unless we ensure every child has a decent start in life.
"We will not succeed as a country if parents can't get to work because they can't get the childcare they need.
"We will not succeed as a country if we waste resources by allowing Sure Start centres to be idle, empty or even close.
"So we're going to put the lights back on, get the kids back in and restore the founding purpose of Sure Start."
The proposals would cost no money, he suggested.
"It is purely a question of political will and leadership. The Government seems content to sit back and let Sure Start wither away.
"If the Tories win a second term, I fear Sure Start will disappear in many parts of our country and one of the great progressive programmes will be lost to the next generation.
"Labour created Sure Start. Labour cares about Sure Start. Labour will save Sure Start."
The party said figures it had obtained via freedom of information requests showed that at least one in six Sure Start centres has reduced its opening hours; one in ten provides fewer services and one in five has fewer staff than in 2010.
Anne Longfield, chief executive of 4Children, said around 1,100 centres could provide additional places if given extra support or direction.
"There is a well-recognised shortage of high quality childcare places in areas of disadvantage which children's centres are clearly able to respond to.
"We urge local authorities to examine the potential for more childcare places in children's centres and work with partners to deliver them. This will reinstate the childcare that many ceased to deliver when the requirement to provide was removed in 2011."
A Conservative spokesman said: "Once again Labour are shaking the magic money tree to pay for unfunded spending commitments. That's exactly how Labour got us into a mess in the first place.
"Hardworking people will pay the price for Ed Miliband's chaotic ill-discipline through higher taxes, more borrowing and more debt."
The party said the original Sure Start programme " was unviable" with more than half of centres found by a spending watchdog in 2009 to be operating at a loss and councils complaining it was underfunded.
It also disputed the closure figures, insisting there had been 45 "outright closures" with in other cases managements being merged, and said funding had been maintained .
Ms Longfield said: "It's 14 years since 4Children first called for a Sure Start in every community and we remain as convinced as ever of their immense potential to offer the support needed for families to flourish
"Childcare is one of the biggest financial and logistical challenges for many parents - we know that one in five parents paying for childcare are considering giving up their job or reducing their hours as a result of the financial strain.
"With over 3,000 children's centres across the country, and a third telling us they have space to provide more childcare, there is a huge untapped resource which has the potential to both support parents with the challenges of childcare and give children the best start in life."
The Pre-school Learning Alliance welcomed the initiative but dismissed Labour's suggestion that it could be implemented without any additional public spending.
Mr Hunt claimed that the taxpayer would not bear any of the burden because the extra provision would come from outside providers using existing public buildings and facilities.
Alliance chief executive Neil Leitch said: "It's vital that all children, regardless of background, have access to high-quality childcare and so we broadly welcome plans to increase the availability of childcare places through Sure Start children's centres.
"However, it would be short-sighted to suggest that such an initiative would not require additional funding from government.
"Research has shown that the free entitlement offers for two-, three- and four-year-olds are already substantially underfunded. As such, this longstanding issue would need to be tackled before any requirement on children's centres to deliver childcare could be imposed.
"It's also important to remember that children's centres offer more than just childcare - they are a vital source of information, advice and support for parents and families.
"Any plan to expand the use of children's centres would therefore need to take into account the need for adequate funding not only for high-quality childcare provision, but also the improvement and sustainable delivery of family information services."