As a basic statement of fact it is true, I agree with it and I think most people would.
However, like a lot of mumsnetters I am in a full time salaried post. I get paid the same whether my work takes me ten more hours or ten fewer hours than I am contracted for. I live in an economically successful part of the country, and there are other jobs like this available should my current one disappear. My employer happily makes (sometimes quite expensive) reasonable adjustments for employees.
If people are just lazy, again everyone can agree they should work full time. The problem comes for two groups. Firstly, people who have health conditions that would require reasonable adjustments but find that the employers they can apply to won't make them, leaving them working fewer hours than they could.
Secondly, those on short hour contracts, who find that they can't take additional work as their employer requires them to be available to work extra hours at very short notice maybe a few times a year. Again, they are working fewer hours than they would like.
I'll find any politician credible who can come up with sufficient carrot and stick for both employers and workers to solve these situations. Just saying things we can all agree with doesn't cut the mustard, I'm afraid.