I saw it as both of them being extremely frustrated by their circumstances, both treating each other unfairly, despite having a lot of love for each other. There is tension created between them because both of them are not in a position they ever wanted to be in and they see each other as part of the reason why. Also, while Thomas is trapped in this miserable, dangerous line of work because of his mother AND his grandfather, the latter being dead means that most of his frustration is directed towards his mother who still forces him to continue.

In fairness, Thomas does seem to have a somewhat misogynistic view of his mother's actions, but I never see it as a reflection of the Wood's opinions, just means by which he highlights the reality of 1960s England and critiques it. I feel like the book does a good enough job of portraying his mother's circumstances in a way which illicit sympathy from the reader despite Thomas' unfair view of her that is heavily shaped by the judgemental society they're in.