The chancellor was accused of a cover-up the impact of her national insurance raid on the workers.

While all tax policy changes are accompanied by an impact assessment known as a Tax Information and Impact Note (TIIN), the government did not publish one alongside the £25 billion National Insurance raid on employers announced in budget, appeared.

TIINs assess the likely impact of a policy change on the economy on families, individuals, equality groups and those with characteristics protected by the Equality Act.

Before the general election, Labor repeatedly pledged not to raise taxes about “working people”, including in his manifesto.

said the chancellor the budget fulfilled the labor commitment because NI increases fell on employers, not on employees’ payslips.

However, the independent Office for Budget Responsibility’s forecast accompanying the budget said 80% of the NI increase would be passed on to workers through lower pay rises, while the other 20% would be felt through higher prices.

Last week, the Institute for Fiscal Studies think tank warned that the policy would have a disproportionate impact on women in the labor force, as they are overrepresented among the lowest wage earners are likely to be most affected by the change.

Mel Stride, the shadow chancellor, said: “It is unacceptable that Labor should withhold this critical analysis of the impact of yet another pernicious policy of theirs.”

A policy impact assessment is expected to be published in the coming months when the legislation is implemented change of national insurance is drafted.

Government sources said the long delay between announcing the policy and publishing the impact assessment is a result of the changes not coming into effect until spring 2025.

It comes after the Government was accused of “breaking the rules” by failing to publish them equality impact assessment of winter fuel allowance changes.

The government was forced to release the document following a freedom of information request. It revealed that seven out of 10 disabled pensioners had lost their winter fuel payments due to the Chancellor’s allowance cuts, according to their own forecasts.

The Tories described the disaster as “appalling” and suggested Ms Reeves had breached the ministerial code.