Officials have sought to allay concerns that the Greater Bay Area plan will allow some mainland hospitals to transfer their patients to Hong Kong facilities, saying this will be only for SAR residents.
But some pan-democratic lawmakers remained unconvinced.
Opposition lawmakers and a patients' concern group had raised fears that such a move would swamp public hospitals in Hong Kong, which are already creaking under an increasing load.
During the Chief Executive's monthly question-and-answer session in Legco, Civic Party lawmaker Kwok Ka-ki said medical staff working at public hospitals in Hong Kong are already enduring extreme misery.
He questioned whether the government had consulted the medical sector to see if they agreed with initiatives proposed in the blueprint released by Beijing.
But Carrie Lam said the transfer arrangement is merely aimed at helping Hong Kong people living on the mainland to come back for medical treatment.
"I need to clarify that the non-emergency patients mentioned in the blueprint refer to Hong Kong people," she said.
But Kwok told RTHK's Timmy Sung he was not convinced.
"I couldn't find [anything in] black and white from the papers stating that the provision of the services can only be enjoyed by people of Hong Kong. We have all the facts pointing that all these measures will only add more to the burden on the people and the medical profession of Hong Kong," he said.
Democratic Party lawmaker Helena Wong pointed out that many parts of the blueprint are unclear. She urged the government to promise that services at public hospitals would only be reserved for Hong Kong people.
Speaking to reporters, the Health Secretary, Sophia Chan, also said the transfer suggestion had been made in response to the demands of Hong Kong people living on the mainland for "better transportation".
"The focus is really on Hong Kong people who live in the Greater Bay Area. That transfer suggested is in fact just a suggested measure. It's really for Hong Kong people," she said.
A chapter named "Building a healthy bay area" in the blueprint released on Monday only mentions that the authorities should study launching services to transfer non-emergency patients for "cross-border treatment" at designated public hospitals.