What is not clear to me is whether the pension lump sum would be used to pay the deposit (in which case, that's nothing new, as parents can already do this if they want to) or merely guarantee the mortgage - again nothing new, I know lots of people who have done this for their children.
I don't see that the pension lump sum is any different from any other savings parents might have - except that if you take your lump sum and spend it on anything, whether it's home refurbishment, a holiday, or helping your children, your pension income will be significantly less than if you leave it in your pot.
He is talking about people with a pension pot of £40K which at current rates will provide an income of about £2400 pa if you're lucky.
Presumably it has not occurred to the Lib dems that if people significantly reduce their pension income, they will then qualify for more state benefits like pension credit and housing benefit...........