Just one in three voters would oppose a hike in the rate of employers’ National Insurance in the Budget, HuffPost UK can reveal.

In a major boost for the government, a poll by the More in Common think-tank also found that the same proportion of the public do not believe the move would break Labour’s election manifesto.

A row erupted this week after ministers repeatedly refused to rule out an increase in the employers’ rate of NI, a move which could raise £17 billion for the Treasury.

Labour’s manifesto said the party “will not increase taxes on working people, which is why we will not increase National Insurance, the basic, higher, or additional rates of Income Tax, or VAT”.

According to the More in Common poll, only 34% of voters think the move would break that pledge, compared to 47% who do not.

Asked whether they would support a rise in employers’ NI, only 34% said they opposed it.

A total of 29% back the policy, while a further 26% of voters said they were neutral about it.

Luke Tryl, More in Common’s UK director, said: “While the Conservatives are trying to suggest a potential rise in employers’ National Insurance would breach their manifesto commitment, the public aren’t buying it and are more likely to say the pledge only applied to employees’ National Insurance.

“With only a third of voters saying they’d oppose a rise in employers’ National Insurance, for now at least it seems like raising the tax would be some low-hanging fruit for Labour as they seek to put together a budget that balances the books without a return to austerity.”