With days to go before the general election, Jeremy Corbyn endured a tough interview live on the radio while launching a major policy on childcare.
Under the new plans, Labour want to extend the provision of 30 hours of free childcare a week to all two to four-year-olds.
But while being questioned on 30 May by Emma Barnett on BBC Radio 4's Woman's Hour, the Labour leader was left flustered and lost for words has he failed to produce the numbers for this new scheme.
Emma Barnett: How much will it cost to provide unmeans-tested childcare for 1.3 million children?
Jeremy Corbyn: It will cost... erm... it will obviously cost a lot do to so, we accept that.
EB: You presumably have the figures?
JC: Yes, I do.
EB: So how much will it cost?
JC: I'll give you the figure in a moment
EB: You don't know it.
EB: You're logging into your iPad here. You're announcing a new major policy and you don't know how much it will cost?
JC: Can I give you the exact figure in a moment?
EB: You're holding your manifesto, you're flicking through it, you've got an iPad, you've had a phone call while you're in here and you don't know how much it is going to cost.
JC: Can we come back to that in a moment?
EB: What, when you've looked it up? My point is, this is quite troubling. This is a policy you're launching today, Mr Corbyn, and you don't know how much it's going to cost. It hardly inspires the voters.
JC: I think what is important for the voters to understand is that if we don't invest in our children and we don't invest in them for the future then they do less well in primary school, less well in secondary school and less well in the future.
EB: But you don't know the cost?
JC: I want to give you an accurate figure.
EB: Why on Earth are you giving free childcare to people who can afford it, if it's un-means tested? You don't have the figure. Hopefully somebody's emailing it to you.
JC: The important thing is that all children get a chance to grow up together. At the moment we have a system which separates out in the sense that a child of wealthy parents may well be able to go to a paid-for pre-school or nursery facility; others will not get that chance because their parents can't afford it or if they're poorer will get a free place. What we think-
EB: This is a very expensive policy, Mr Corbyn. I'm going to help you out with the figures. Would you like to hear how much it's going to cost?
JC: What we think is, it's more important to invest for the whole community and collect the money back through taxation on the principle of universalism.
Eventually, Ms Barnett quoted shadow education secretary Angela Rayner, who was on BBC Radio 4's Today programme earlier: "£2.7bn, then £4.8bn... with half a billion to reverse cuts to the Sure Start scheme. Does that sound about right?"
"It does sound correct," Corbyn said.
The announcement was part of Labour's manifesto proposal to extend the 30 hours a week of free childcare to all two-year-olds - a policy which is part of Labour's plans for a National Education Service.
The policy would benefit more than 1.3 million children as complex rules mean only 40% of two-year-olds qualify while many working parents with three and four-year-old children are missing out, according to Labour.
Sounding exhausted at times, Corbyn was repeatedly pushed on his ability to lead the country as well as if he would step down should Labour lose the election on the 8 June.
He wasn't drawn into discussing resignations, instead insisting that he would win the election.
It came just hours after both he and Theresa May faced members of the public and Jeremy Paxman as part of a live televised debate.
Lib Dems were quick to react to the radio appearance. Former MP Alistair Carmichael said: "Jeremy Corbyn has had two 'brain fades' in two days. It seems he's been borrowing Diane Abbott's calculator.
"Jeremy Corbyn's Labour let people down by voting with Theresa May on Brexit and now is failing to say whether they will help those struggling families who stand to be most affected. Working families on tax and child credits risk seeing their incomes slashed by hundreds of pounds in the years ahead as prices in the shops rise," said Carmichael.