I'm not speaking for everyone on Mumsnet.
I've explained the factual distortions in the tax system that are disincentivising work for the people who pay most of the UK's tax (not the super rich!) resulting in low UK productivity and tax revenues and therefore no money to improve public services etc for everyone. This is fact. Hunt's own research stated this. The IFS have said it's a "dog's breakfast". The Times and FT and Guardian and others have written articles about it. So yes of course higher earning people cut down their hours because it's not worth them working more. This is factual and is happening across the economy, research shows it clearly and indisputably. This is bad for everyone.
I have also explained how single parents (almost all women) are doubly impacted by this, giving the example of my own situation, because these tax thresholds are doubly punitive for us. Others in the same situation have also said so, on this thread and in the research. We pay huge amounts of tax and can barely afford to live because the UK tax system applies all of these thresholds on an individual not household basis, impoverishing us and our children. So for us, even less incentive to work more and actually, unsurprisingly, many do not bother or give up entirely.
I've seen the calculations. If I'd never bothered at all, with degree and professional qualifications and all the hard work to build a career and buy a house and instead claimed benefits we would have TWICE the disposable income per month that we do now. That is disgusting.
I want to work. I want to contribute. I always have done so. I should however be left with enough to provide my children with a decent life, when I'm paying £34k per year into the pot to help other people. And to be able to take a promotion without us then having LESS money per month than we do now and being unable to pay my mortgage.
If you want a country where there's money to pay for services and benefits then making it impossible for higher earners to better their circumstances by working more - while bettering everyone else's at the same time by paying even more in - then penalising them to the extent that it's not worthwhile for them to work is not a good idea.