The government has dismissed fears that the health care voucher scheme for the over 65s will be open to abuse once married couples are allowed to link their balances and share the funds between them.

Acting Health Secretary Libby Lee confirmed in Legco on Friday that couples will only need to make a declaration when they register to tie their vouchers together, and won't have to prove they are married.

Lawmakers raised concerns that this could lead to abuse of the scheme, just as the voucher amount is set to increase from HK$2,000 to HK2,500 per person per year.

"If there are two single elderly people, can they possibly declare they are married to utilise these shared use of medical vouchers?" questioned Kowloon Central councillor Kitson Yang.

“Maybe your ID has been registered by someone else. How can you guard against any potential abuse?” asked Election Committee member Yan Chan.

In response, Lee said measures will be in place to prevent abuse.

“They have to show a copy of their spouse's ID. Once they use the vouchers there will be an SMS message to be sent to them and their spouse. We will also monitor any unusual registers,” she said.

Married couples are expected to be allowed to start sharing their vouchers from next month.