Under the scheme, first-home buyers can be approved for a mortgage with as little as a 5 per cent deposit, and the government will guarantee up to 15 per cent of the loan.

Usually buyers with less than a 20 per cent deposit must pay lenders mortgage insurance, a cost that can delay their entry into the property market.

The scheme has been taken up by 20,000 buyers since starting at the beginning of the year, and there will be another 10,000 spots in the extended program.

Coming into effect on budget day on Tuesday, the extended scheme will be tweaked to only include new homes or newly built homes, a move that is designed to support the residential building industry.

Caps on the value of homes that can be bought under the scheme will also be increased. The maximum amount that can be borrowed in the ACT to increase to $600,000, up from $500,000.

In regional NSW, the cap has been increased from $450,000 to $600,000, and in Sydney and regional centres it is now up to $950,000. For regional Victorians, the cap has been increased to $550,000 from $375,000. The government hopes these moves will make the program available to more people.

The current scheme is available through more than 25 lenders, and the the National Housing Finance and Investment Corporation is set to confirm which lenders will participate in the extended scheme.

The scheme can also be combined with the HomeBuilder scheme, and the First Home Saver Scheme.

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Treasurer Josh Frydenberg said that under the HomeBuilder scheme, people could get a $25,000 grant from the government for home renovations or new builds with a value up to $750,000.

"Helping another 10,000 first-home buyers to buy a new home through our First Home Loan Deposit Scheme will help to support all our tradies right through the supply chain including painters, builders, plumbers and electricians," Mr Frydenberg said.

Mr Sukkar said first-home buyers could also be eligible for state and territory grants and concessions, on top of the federal assistance.