She made the comment a day before Britain officially opens application for the new visa scheme, which offers millions of Hongkongers with British National (Overseas) status a pathway to full UK citizenship.
London announced the scheme after Beijing imposed its national security law on Hong Kong last July.
Writing on her blog, Cheng reiterated the Hong Kong government’s decision to follow in the footstep of Beijing, to stop recognising the BNO passport as a form of identity proof from Sunday.
She said people should understand that the 1984 Sino-British Joint Declaration had no clause that provided for British rights or obligations to Hong Kong after the handover.
Cheng also pointed to a 2008 quote from former UK attorney general Lord Goldsmith that said giving BNO holders full British citizenship could be a breach of the declaration.
Meanwhile, the Secretary for the Civil Service, Patrick Nip, was asked to respond to rumours that BNO holders may be banned from holding public offices in future.
He said people should not link the matter with the nationality of government staff.
“As regards to civil servants holding foreign passports and all that, we just follow what is set out in the Basic Law and Hong Kong laws. Basically the requirement is that they have to be Hong Kong permanent residents,” he said.
Anyone with BNO status can apply for the visa, which lets the holder live and work in the UK for five years, and apply for permanent residency afterwards.