gassor
There may be more posts after this.
The IFS are better respected by journalists than by economists: the charge is usually that they can't do macroeconomics. They certainly don't consider the political context of their calculations.
Here's Simon Wren-Lewis on the credibility of Labour's spending plans. SWL's politics are fairly left wing (although he's no Corbynite) but he is very much a mainstream economist.
https://mainlymacro.blogspot.com/2019/11/is-labours-economic-plan-credible.html
Mostly he seems to be holding his breath hoping for the best. Some of it is just disingenuous, "The IFS say the corporation tax numbers are realistic", yes but they say the significant rise in Corp Tax would be very harmful. Has Labour condemned the IFS before, or is just suddenly that Labour has misgivings about the IFS?