The Council of Trade Unions says National's proposed infrastructure fund is a smokescreen for what it calls an unpopular partial asset sales plan.
National is campaigning on plans to sell up to 49% of state-owned energy companies Meridian, Mighty River Power, Solid Energy and Genesis and reduce the Government's stake in Air New Zealand.
It expects this to raise $5 - $7 billion in the coming three years which would be used to build a Future Investment Fund.
Health and education are two areas that would receive money from the fund and National Party leader John Key says some of the profits could also be invested in Kiwibank.
"Personally, I'd rather own 51% of Meridian and have 21st century schools than I would actually own 100% of it."
Council of Trade Unions economist Bill Rosenberg rejects the idea as a smokescreen to disguise the fact that asset sales are very unpopular.
"If they wanted to set up an infrastructure fund they could do that at any time but to pretend that the money comes from this particular source of funds is really just an accounting exercise that's setting up jam jars for funds they were going to spend anyway."
Labour has dismissed the partial asset sales plan as a cheap trick, while the Green Party says the idea is the most expensive way ever devised to pay for new infrastructure.
Green Party co-leader Russel Norman says the idea of privatising state-owned assets to pay for schools and hospitals is "completely bonkers"
"The Government's proposing that instead of borrowing at 6% they will sell these assets earning 15% - you can understand what economic illiteracy it really is."
National's plan would also put money towards earthquake-proofing and repairing leaky schools.
Secondary Principals Association president Patrick Walsh says the leaky building problem alone could bear a $2 billion price tag.
He says that if detractors of National's plan talked to principals, boards of trustees, students and parents they would discover that there is a huge shortage of money available to ensure quality education delivery.
Mr Walsh says that without the money there will be a deterioration in the school building network which will compromise children's learning. "It's not for me to comment on where the money should come from - that's a political decision," he added.
Meanwhile, National says it would set a high bar for projects to receive funds and ministers would make those decisions as part of the annual budget round for at least the next five years.
A spokesperson for National's Bill English says the money would not be invested, because it would move in and out of the fund regularly. Specialist fund managers would not be needed and the Treasury would oversee the fund.