Under the new home deposit scheme, the government would offer loan guarantees for first home buyers, allowing them to buy properties with deposits of just five per cent instead of the typical 20 per cent.

The prime minister unveiled the plan on Sunday, with Labor blunting his pitch on housing affordability by matching the commitment.

But Mr Morrison says Labor's support comes as it plans to scrap another scheme that helps people save for their first home by withdrawing voluntary contributions to their superannuation.

Housing prices would also fall under a Labor government as it rolls out proposed changes to housing tax breaks, he argues.

"I want to see people when they buy their first home, to be able to stay in the market and keep the value of the home that they've bought," the Liberal leader told reporters in western Sydney on Monday.

Asked whether his own plan might increase prices, the prime minister wasn't sure.

"It's difficult to say, it's difficult to say," he said.

"But I do know this: Labor's housing tax will force the value of your home down."

Labor says it still wants to see the details of the plan, but gave it a tick quickly because it's modest.

About 10,000 people earning up to $125,000, or a couple earning $200,000, are expected to benefit each year, which would have been about one in 11 new home-buyers in 2018.

But Mr Shorten says the scheme doesn't go far enough, with his planned changes to the negative gearing and capital gains tax needed.

"If you want to tackle housing affordability, it's only part of a much bigger picture," he told reporters on the NSW central coast.

"That's why we need to reform the unfair playing field, where property investors are getting subsidised by the Morrison government to buy their sixth or seventh house."

The government is providing the National Housing Finance and Investment Corporation with $500 million to deliver the scheme, along with $25 million to set it up and research the housing market.

There were about 110,000 new home-buyers in Australia in 2018, the highest level in nine years.

Housing industry bodies the Property Council and Master Builders have backed the proposed scheme.

Financial comparison site RateCity has urged people to be cautious about signing up to a 30-year mortgage with a thin deposit.

They say people with a five per cent deposit could end up paying more than $50,000 extra in interest than those with a 20 per cent deposit on a $500,000 purchase, based on an average interest rate of 4.31 per cent.

The plan is based on another program already operating in New Zealand.

But across the Tasman, first home-buyers must save a deposit of 10 per cent, rather than five per cent, before they are eligible to have their loan underwritten by Housing New Zealand.

Australian Associated Press