Lam said on Tuesday that Hong Kong recently had 479 district councillors, but 260 of them have since resigned, and another eight have been disqualified for reasons such as being arrested and detained or having left Hong Kong.
A total of 211 councillors who are still serving will be asked to swear allegiance in four batches, Lam said, adding those who refuse to attend the ceremonies will lose their seats.
She said invitations will be sent later on Tuesday for the first ceremony, to be held for Hong Kong Island councillors on Friday at the North Point Community Hall.
Lam said she had appointed Home Affairs Secretary Casper Tsui to be the oath administrator.
She said Tsui would not declare the validity of the oaths immediately.
“After the ceremony, we will not immediately announce whether the oath is valid or not. But for councillors whose oaths are valid, they will be notified afterwards that they will continue to be the SAR’s district councillors,” Lam said.
“For some, if we have doubts and do not fully trust their pledge of loyalty, they will be given a chance to explain themselves. The oath administrator will then make a judgement, and if necessary, he or she can seek further legal advice to support the final decision,” she added.