Reeves said she is asking "ordinary people to pay a little bit more" after she announced tax rises of £26bn to come into force by 2030.
Setting out her Budget in the Commons earlier, she said that income tax thresholds would be frozen until 2031, while the two-child welfare cap would be scrapped.
A spokesman has said the chancellor has confidence in the head of the Office for Budget Responsibility, Richard Hughes, after the watchdog mistakenly published details of the Budget early.
