Mrs May says she is not planning to have a snap General Election as had been speculated, as it "would not be in the national interest".
"What was clear in the Budget yesterday is we have fully funded that. extra money into our NHS and not raising taxes". It found there are now 900,000 more people in the higher rate tax bracket than if the 2010 threshold was maintained in line with inflation.
The IFS director described other tax changes introduced by the Chancellor - including a digital service tax on online giants and a cut in business rates for small retailers - as "a short-term sticking plaster solution to some big underlying problems with the tax system".
Asked whether this was the case on ITV's Good Morning Britain he said: "I hope not".
"We would take appropriate fiscal measures to protect the economy, to prepare us for the future and to strike out in a new direction that would ensure that Britain was able to succeed, whatever the circumstances we found ourselves in".
But these increases will now come into effect 12 months ahead of schedule at the start of the next tax year on April 6, 2019.
A freeze on Spirits Duty will save 30p on a bottle of Scotch compared to the inflation assumption in the Office for Budget Responsibility's forecast, the Chancellor said.
India makes major strides in improving business prospects
As a result, the time needed for exporters to comply with documentation requirements was reduced to 14 hours, from 38 hours. India was ranked 80 in easing the process of cross-border trade, 163 in enforcing trade and 108 in resolving insolvency.
Labour MP Chuka Umunna told ITV's Peston: "No, I don't think these are the right kinds of things to be basically making a set of income tax changes which primarily benefit high earners".
Mr McDonnell dismissed the Chancellor's claim austerity is coming to an end as he insisted it is "rolling out still".
"Theresa May promised the people that austerity would end, but this budget has delivered nothing of the sort".
The tax would raise £400m per year by 2022-23.
But he said agreement with Brussels would result in a "deal dividend" for the economy.
"This shows we are serious about this reform", he said.
The Chancellor set out a five-year plan for departmental spending which will see Whitehall budgets rise by an average of 1.2% a year.