If that assumption is that taxes do fund spending then that is logically not true, and functionally not true.
If you’ve already made your assumptions, not sure why you’re now asking me questions. But if you do believe that taxes fund spending, then to increase spending you have to increase taxation (or borrow more, or sell off assets, which is unsustainable in any economic model). But increasing tax to fund spending is as heterodox as saying taxes don’t fund spending. The currency orthodox position determines that tax does fund spending and any spending is a bad thing that causes inflation and stifles the economy. Most relevant to this point is that Tax rises are the slippery slope to totalitarianism. It is an orthodoxy that both Labour and Tories subscribe to.
While I am happy to go with the heterodox option to tax the rich on the grounds that at least it isn’t orthodoxy, the only party explicitly promising that position is the Greens.