One reporter claimed he was grabbed by an official when he tried to ask a question, while another said he was shoved.
Lacson said he was not aware of the incident and urged the reporter to file a formal complaint so it could be investigated.
“My point is that this is not acceptable so please raise this issue formally so we can address it.”
Lacson defended the decision not to allow reporters to question the prime minister.
“We’re really proud of the fact that we’re very accessible to journalists and media in New Zealand and that’s important – it’s an important part of our democracy,” he said. “But we also have to respect that as hosts to countries coming to New Zealand and/or when we’re overseas, there are different protocols. That doesn’t mean I can answer every question you want.”
Meanwhile, in Australia, Prime Minister Anthony Albanese expressed concern about PM Lee’s treatment of journalists in Parliament at a signing ceremony earlier this week.
Chinese authorities tried to prevent journalists from observing Mr Albanese and Mr Li signing the agreement.
“Australian authorities naturally intervened and asked the Chinese officials who were attending the press conference to move and they complied,” Mr Albanese told ABC Australia on Wednesday.
“Australian journalists should not be impeded from carrying out their jobs and we have made that clear to the Chinese embassy.”