The High Court yesterday gave the Attorney-General's Chambers (AGC) permission to continue with contempt of court proceedings against Mr Li Shengwu over a Facebook post he made on the judiciary.
Senior State Counsel Francis Ng told reporters the AGC has until Sept 4 to file the required documents.
Mr Li - the eldest son of Mr Lee Hsien Yang and nephew of Prime Minister Lee Hsien Loong - will be given all the documents for him to respond, said an AGC spokesman.
This latest development coincided with a Facebook post Mr Li, 32, made yesterday about an Aug 8 letter he received from the AGC, which asked him to apologise for his July 15 post.
In this earlier post, the junior fellow at Harvard University wrote that the "Singapore government is very litigious and has a pliant court system", and said foreign media had been cowed into self-censorship because of previous legal action.
The post was related to the dispute between his father and aunt Lee Wei Ling on one side, and his uncle on the other, over their late father's home at 38, Oxley Road.
The AGC called his post an "egregious and baseless attack" on the judiciary, and applied to begin contempt of court proceedings against him on Aug 4.
The application was heard yesterday in chambers, which meant the hearing was not open to the public.
On the same day, Mr Li said on Facebook the AGC had "privately revised its demands", and posted its Aug 8 letter and his response.
The AGC had asked Mr Li for an apology and an undertaking not to repeat his allegations, while noting he had amended his July 15 post.
In response, Mr Li wrote: "The truth matters: I cannot confess to a crime I did not commit in return for a discontinuance of the legal proceedings against me."
He also said he was not responsible for the widespread publication of his post which was set to the "friends only" privacy setting, and asked the AGC to take action against local mainstream media for republishing what he wrote.
He added that PM Lee's press secretary Chang Li Lin had, "curiously", been aware of AGC's revised demands and disclosed them to the public on Aug 18.
He was referring to her comments on an interview he gave Reuters, in which he said he left Singapore because of concerns that he might be detained by the authorities.
Yesterday, Ms Chang said in reply to media queries that Reuters had asked the Prime Minister's Office (PMO) if the allegations Mr Li made were true .
"My office checked with the AGC and was told not only was Mr Li's claim that he might be detained inaccurate, AGC had in fact offered to drop the charges if he were to apologise and withdraw his statements.
"AGC received a subsequent query from Reuters on the same matter and asked Reuters to refer to the PMO's statement," she said.
In his latest letter, Mr Li also disputed an earlier AGC statement that it had received his response after its extended deadline of 5pm on Aug 4.
He said: "My response letter was hand-delivered to AGC at 4.40pm on Friday, 4 August. This will be borne out by the footage from AGC's security cameras."
Mr Li sent it a five-page letter on Aug 4, which he uploaded on Facebook as well. In it, he wrote that the AGC had misunderstood his private post, adding he had amended it to remove any misunderstanding, but would not take it down.
Among other things, Mr Li said his criticism was directed not at the judiciary but at the Singapore Government's "aggressive use" of rules like defamation laws to constrain reporting by international media.