National Party finance spokesperson Bill English has claimed the party's tax cuts would put between $7 billion and $8 billion into the economy from next April.
Mr English made the claim during a debate with the Labour Party's finance spokesperson Michael Cullen on Nine to Noon.
He said the tax cuts are an essential part of National's response to the economic slowdown and would come at just the right time.
"Cutting taxes on 1 April, that will put an injection of somewhere between $7 billion and $8 billion into this economy which at the moment it is not going to get," he said.
Dr Cullen said the National Party had costed its tax policy at $3.7 billion.
"Bill's just claimed $7 billion or $8 billion going in (on) 1 April next year. Tax cuts next year don't add anything like $7 billion to $8 billion into the economy."
Mr English said he would have to check the figures.
On the National Party's website it estimates the cost of its tax cuts at $1.29 billion next financial year and $1.83 billion the year after.