At a press briefing here, Lam was responding to Hong Kong protesters' call for the US Congress to pass the Hong Kong Human Rights and Democracy Act, reports Efe news.
"The Hong Kong government strongly disagrees with the US Congress meddling in Hong Kong's affairs through the bill," Lam said. "We express deep regret over that."
"The parliament of any country should handle domestic affairs.
"It is extremely inappropriate for a foreign parliament to interfere with Hong Kong's affairs via any means," she added.
The Act, recently introduced by some American legislators, requires Washington to assess annually whether Hong Kong is autonomous enough to justify its special trade status.
Failure to certify would mean the city would lose certain trade-related privileges with the US not enjoyed by China.
On Sunday, hundreds of thousands of demonstrators marched to the American consulate in Hong Kong, urging the US government and congressmen to pass the bill, which they believe would safeguard their freedoms.
There are about 85,000 American citizens living in Hong Kong.
Some 1,400 US companies have their regional offices or regional headquarters in the Asian financial hub, which is currently in the grip of its worst political crisis in decades.
The crisis, which entered its fourth month on Monday, was sparked by a bill proposed by Lam's administration that would have allowed suspects in Hong Kong to be extradited to mainland China to face trials in courts.
The protesters' demands have since morphed into broader calls for democratic reforms, accountability for police brutality and greater independence from Beijing, as well as Lam's resignation.
On September 4, Lam announced the bill's formal withdrawal, although activists said the gesture came too late and was not enough to satisfy their aspirations for change in the city.
( With inputs from IANS )