Development Secretary Bernadette Linn on Thursday defended the higher price tag for the government's artificial islands project, saying she expects the revenue generated by the plan to be higher than the estimated cost.

Authorities have raised the projected cost for the artificial islands off Lantau Island to HK$580 billion – up from the HK$500 billion predicted in 2018 – while they expect to earn HK$750 billion from auctioning off land sites to developers.

But Linn told a Legco panel that the cost is not the only factor the government considers when pushing forward with development projects.

"When it comes to infrastructure, we should not only have eyes on the [price] and take it forward only when it's profitable. This development project is a long-term investment for the future of Hong Kong, so we should not just have eyes on land sales revenue, but rather the economic benefits that will arise from the development," Linn said.

She added that one-third of the cost will be used for reclamation, while around half will be spent on building road links and railways.

Some lawmakers have questioned the project's price tag, with New People's Party chairwoman Regina Ip calling the forecast for land sales "too optimistic".

"The expenditure estimate and land revenue receipt estimate are very crude at this stage. I think they [authorities] are too optimistic. Other colleagues also referred to other risks, whether we can afford both Northern Metropolis and the artificial island plan at the same time, and whether the economic benefit is justified for this mega project," she told reporters after attending the panel.

When asked about whether authorities would consider bridging the islands with nearby Peng Chau, Linn said her team would study the possibility of building road links to benefit Peng Chau residents.

The development minister added that further research is needed to ascertain exactly how much the project will cost, and that officials aim to report the updated cost to Legco in 2024 before seeking funding from lawmakers.