HOW much cold hard cash are we prepared to spend helping working mothers do what’s right for their children?

That debate is burning with the ferocity of a jet engine following the decision of New Zealand’s Prime Minister Jacinda Ardern to take an extra plane flight so that she can spend more time breastfeeding her 11-week-old baby.

An air force plane dropped off the deputy PM Winston Peters at a Pacific Islands meeting on Monday and then returned to New Zealand to pick up the boss, allowing her to attend for one day instead of three. Estimated cost to the taxpayer: £40,000.

Ms Ardern says she tried to do it cheaply. She looked at hitching a lift with the Aussies, but it didn’t work out, and she can’t take baby Neve with her because she’s too young to have the necessary vaccinations. That meant she had to choose between going for a short time or not attending at all, observing that if she didn’t go, she’d be criticised for that too.

There was of course a third option: she could have gone for the full three days and left her baby to be bottle-fed at home by dad, as social media users indignantly pointed out.

But Ms Ardern is a millennial. She is a woman who came to high office in the wake of third-wave feminism. She looks around her and sees men everywhere pursuing their ambitions without feeling as if they are failing their children by doing so, and she sees no good reason why she should not do the same. She is a willing trailblazer – only the second world leader after Benazir Bhutto to give birth in office – and is not afraid to be a world-leading social experiment. With her decision to spend money on an extra flight, she is demonstrating that equality does not mean being the same, but being willing to accommodate differences, and that accommodating differences can cost money.

I don’t know what she would say to those who think she should leave her breastfeeding baby for three days, but I imagine she would point out that bottle-feeding means either abandoning exclusive breastfeeding and giving formula instead (which she may not wish to do), or expressing copious quantities of milk before leaving, which is fine in theory but very difficult to achieve in practice. Perhaps her young baby won’t even take a bottle (many don’t).

No; this is a woman who may be prepared to make sacrifices for herself, but not for her baby, and she certainly has my respect for that. Hundreds of thousands of women will identify vividly with her dilemma, torn between being the mother they want to be and the professional they want to be. And the reaction she has faced underlines to what extent women are still fighting the battles of the past.

It’s all seemed very un-Kiwi-like. New Zealand may be a trailblazing young liberal of a nation, blissfully free from the albatross of history, but the opposition to Ms Ardern’s extra flight has been decidedly Old World. It reveals a deep-seated unease about a woman with a baby doing a big important job. Everyone wants equality, unless there’s a cost attached. Everyone wants equality, so long as women behave exactly like men. As one Twitter critic fumed, “she swore having a baby would not interfere with doing her job. It already has…. Many people feel lied to, and justifiably so”.

Sigh. What this sort of attack amounts to is the age-old argument that if a woman can’t be just like a man in the way she conducts herself in a high-powered job, then she is not fit to do it. The protests at taxpayer money having to be spent to accommodate her needs as a mother echo the protests of 40 years ago from companies hostile to paying maternity benefits. The sky did not fall in then. Businesses were not drained of profit by employing women; indeed, the opposite is true. The female workforce is now essential to national economic prosperity, which is why successive governments have bent over backwards to encourage more women to work for longer.

Ms Ardern’s extra flight will only claim a small proportion of the overall ministerial travel budget and is likely to be a one-off in any case. Soon baby Neve will be old enough to be vaccinated for travel and then there will be no problem with the New Zealand Prime Minister travelling overseas. But there will be other work-life dilemmas. What if there’s a bad bout of childhood infection? Hopefully, Ms Ardern will handle that with the same cheerful decisiveness she has shown this week and be prepared to miss a meeting or two.

Will she be failing as Prime Minister by doing so? Will she be showing her critics that it can’t be done, being a new parent and a national leader? No: she will be showing that there is another way of doing things, a different way – a better way. Where women like Ms Ardern lead, men as well as other women, will follow. A culture change is taking place and we’ll all benefit in the end.