The man put in charge of a major review into workers rights and the rise of the gig economy has called the chancellor's election pledge-breaking rise in National Insurance for the self-employed "progressive" and "economically rational".
"As tax rises go, this is broadly progressive," said Matthew Taylor, the head of the Royal Society of Arts and former advisor to Tony Blair when he was Prime Minister, speaking on the BBC's Sunday Politics show.
"There's a lot of self-employed people on low incomes and they will actually be better off. I think it's economically rational because the reason for that difference in National Insurance contribution was to do with state entitlements... last year the self-employed got pensions, [and] the government's consulting about paid parental leave."
He added: "Self-employment is growing, people are choosing it, they like the autonomy, the flexibility, but it erodes the tax base and it's important to address those issues."
The Taylor review will have a broader frame of reference than taxes, however, and will look at the quality of work in the British economy, he said.
"At the hearty of what I'll be proposing is a set of shifts that will improve the quality of that work so that we have an economy where all work is fair and decent and jobs give people the scope for development and fulfilment. This issue of tax is a small part of that."
The rise in National Insurance for the self-employed, whose numbers are nearing 5m, has caused a political backlash, with Philip Hammond accused of breaking an election pledge not to raise the tax.
An influential economic think tank last week called the rise modest but welcome.