Finally, a budget that mentions childcare. But where will these magic nursery places come from, Jeremy Hunt?

Wednesday’s budget announcement represents the largest expansion of free childcare England has ever seen, and from a Tory government. I can’t believe that I actually typed that sentence. Extending the 30 free childcare hours to children aged nine months to two years will cost £4bn and will, the chancellor claims, cut families’ childcare costs by 60%. Combined with the intention to increase the availability of wraparound care for parents of school-age children, it could be the news that many campaigners and parents have been waiting for.

When you live in the UK and you start thinking about having a child, or are perhaps already pregnant with one, there is, I think, a moment when you look into what the childcare offer is and realise, with a sinking heart, that between the ages of nine months and three years old you’re basically on your own. Although it’s often necessary to work full-time, as most modern households require two incomes. So unless you have family support, you’re going to need to pay someone if you wish to return to the workplace. And with the second most expensive childcare system in the world and nursery waiting lists that can last years (one couple I know just paid £14,000 upfront for a child that has yet to be conceived but don’t worry, they refund you if you don’t get pregnant): good luck!

This childcare gap has never made any sense politically, socially or economically. I can remember thinking that I might have to simply give up my job, as many women do. That there has now been political recognition of the unfairness of this, and the burden that it places on mothers, is no small thing. And it is usually mothers, as we all know. The financial pressures on families – of which my colleague Lucy Pasha-Robinson wrote starkly last week – won’t end, but they will be eased significantly in some cases.

So there is something to celebrate, certainly. Just seeing childcare on the political agenda again feels like a sea change, and it’s OK for parents to feel cautiously optimistic, even if they are frustrated about how long the phased introduction of the free hours will take, because parents are desperate and struggling now. Though the measures will not be fully implemented until 2025, it seems that some families, like mine, with a one-year-old, will benefit from 15 hours from next spring. Not that it’s actually 15 hours, just as it isn’t actually 30 hours. Inexplicably, the government continues to assume that school holidays shouldn’t count, despite the fact that most working parents don’t get those off, so it actually provides 30 hours of free childcare a week for only 38 weeks of the year. When you divide the total number of free hours by the number of weeks in the year, it isn’t quite the offer it initially seems.

So it’s important to retain perspective. England has not suddenly become Finland, with its enviable state-subsidised day care system and its willingness to fund parents who want to stay at home to care for their children. Credit where it’s due, though. Joeli Brearley of Pregnant Then Screwed has been fighting for years for better childcare on behalf of British parents, and without her efforts, it is unlikely anything would have changed. She’s not resting on her laurels, though. “This is a significant moment for childcare,” she tells me. “After years of campaigning by parents and groups like ours, childcare is now top of the agenda for every political party – that is absolutely a moment worth celebrating. However, there are a number of serious issues with the plan.”

Reservations include the fact that the funding paid to childcare providers for the “free” hours is too low, which means more nurseries could close their doors – a disaster in the making considering there will inevitably be an explosion in demand. As Sam Freedman, who co-authored the report Delivering a Childcare Guarantee for the Institute for Public Policy Research thinktank, explained: “nurseries subsidise the too low free hourly rate by charging more for one- and two-year-olds (thus such high prices). If one- and two-year-olds also get free hours then they can’t cross-subsidise. You risk a major supply problem.” Research from the Confederation of British Industry (CBI) estimates that fully funding the existing schemes for three- to four-year-olds and expanding the scheme to one- and two-year-olds would cost £8.9bn.

The big question, as Freedman noted, is where these places will come from in a market that is so dysfunctional. Especially when, I suspect, we may see a mini baby boom as parents who were wondering how they could ever afford another baby realise that it might just about be doable now.

Related: Hunt’s £4bn childcare boost welcomed but fears remain for struggling sector

For those less well off and single parents, the changes to the amount of childcare support universal credit claimants receive and the fact it will be paid upfront and not in arrears are welcome developments. That the free offer only applies to households in which all the adults are working, though, might mean that some children who would really benefit developmentally will miss out. The debate around childcare still largely focuses on the difference it can make to parents in terms of their wellbeing and finances, which is important; but the social and educational benefits to children are often left unarticulated. In fact, childcare should be a children’s rights issue and we should not be denying those children access to the education system. The proposed ratio relaxation, which increases the number of two-year-olds in England that each adult can look after in a childcare setting from 1:4 to 1:5 (as is the case in Scotland), is unlikely to help children either.

“Is it all fur coat and no knickers? In some ways, yes,” Brearley says. “Most of what was laid out in the chancellor’s budget is to be implemented after the general election, so we don’t know who will be in charge of delivering it.” It’s a carrot, in other words. One that looks tasty, and shows that politicians are finally waking up to the fact that they desperately need the millennial vote. “What is so important is that we have changed the conversation. The Conservative party now acknowledges that childcare is key infrastructure for the economy and extending subsidised schemes to all children from nine months old is massive. Labour will be forced to beat this policy, and so the only way is up.”

Though I’m pleased, and the free hours will probably benefit me, the Tories will never get my vote. But then, as a friend said, they wouldn’t get my vote even if Jacob Rees-Mogg offered me the free use of his personal nanny. On balance, however, I think I’d rather entrust my baby to the state-funded children’s centre. One of the few that are left after the Conservative party closed them down. Could we possibly have them back, by the way?

• Rhiannon Lucy Cosslett is a Guardian columnist