China is poised to strengthen a law to require telecommunications and Internet companies to inform on customers who discuss state secrets, potentially forcing businesses to collaborate with the country’s vast security apparatus that stifles political dissent.

The move, reported Tuesday by state media, comes as China continues tightening controls on communications services. It also follows a spat over censorship that prompted search giant Google Inc. last month to move its Chinese site to Hong Kong, which provides broader protection of civil liberties than mainland China.