Lawmaker Peter Koon on Thursday proposed at least doubling the HK$2 subsidised fare for elderly people who use public transport, in an effort to keep the concessionary scheme sustainable.

Latest government estimates show that the policy would cost HK$6 billion in the coming financial year, up 50 percent from this year. The administration said earlier that it would review the scheme.

Reverend Koon told an RTHK programme that the fare should go up to HK$4 or HK$5, noting that public money should be spent carefully especially when the population is ageing.

"Transportation fares have gone up by around 30 percent since the HK$2 scheme was rolled out. Is it feasible that we keep the concessionary fare at HK$2 and don't increase it? I think we should be more realistic when looking at this," he said.

The legislator said public transport operators should also shoulder social responsibility and subsidise at least part of the elderly fares.

Another election committee lawmaker, Chan Siu-hung, said the administration could put in place some restrictions on the scheme, in order to reduce its financial burden.

For example, he said a monthly fare ceiling could be set, meaning those over 60 would not enjoy the concessionary fare once the total fare of their trips exceed the amount.

"Whatever it is going to be - be it a fare discount, a limit on the number of rides or on the fare - I hope the original purpose of the policy can be maintained, which is to encourage the elderly to go out more," Chan said.

The government launched the concessionary fare policy for those 65 or above in 2012 and expanded it to cover anyone aged 60 or above in 2022.