Development minister Bernadette Linn on Sunday said the HK$580 billion price tag for building three artificial islands off Lantau is just a preliminary estimate.

Speaking on a radio programme, the official said study is still ongoing on the 1,000-hectare reclamation project around Kau Yi Chau, and they are in no position yet to give concrete figures on its cost and land sale revenue.

"It is now actually premature to come to a more precise estimate on the works requirement, particularly when we have yet to confirm a lot of the alignment for the transport network, and also we have yet to go into detailed works design," she told reporters after the programme.

She said authorities will give another update on the cost estimate in 2024, but that would still not be the final figure when they ask Legco to fund the works in 2025.

The official brushed aside concerns that there is not sufficient demand for land to justify the proposal.

"I don't agree that we should evaluate whether we need those pieces of land in future only according to our present economic situation," she said, adding Hong Kong will miss out on economic opportunities if it does not have land ready in advance.

Linn said she estimates the project will generate HK$200 billion worth of economic benefits every year when completed, as well as provide better living conditions for Hong Kong people.

The official said she hopes 30,000 homes - as the first batch of up to 210,000 flats - will be ready for people to move into in 2033, adding that the government may consider raising the minimum flat size requirement of 280 square feet in future.