An Egyptian MP was removed from a news conference about jailed hunger striker Alaa Abd El-Fattah after he questioned whether the British-Egyptian was a political prisoner.
Mr Abd El-Fattah's sister, Sanaa Seif, was speaking at an event at COP27 in Egypt's Sharm el-Sheikh when Amr Darwish stood up and started shouting at Ms Seif.
Ms Seif was calling for her brother's release after he stepped up a longtime hunger strike from eating 100 calories a day to no food and he stopped drinking water on Sunday, saying he is willing to die if not released after his imprisonment for "spreading fake news" in December 2021.
The 40-year-old pro-democracy writer and activist has been kept behind bars in Egypt for most of the past decade.
She told the news conference she has asked British authorities to obtain proof Mr Abd El-Fattah is "alive and conscious - I did not get any response".
She added Egyptian President Abdel Fattah el-Sisi told French President Emmanuel Macron he is committed to preserving her brother's health.
"These statements really worry me, are they force-feeding my brother right now? Is he handcuffed in a bed, put on IVs against his will? This is what it sounds like to me," she said.
Mr Darwish took the microphone and spoke at length in Arabic as he questioned why the family describes Mr Abd El-Fattah as a political prisoner and accused his family of resorting to foreign pressure to attack the Egyptian military.
As Ms Seif tried to answer, he refused to give up the microphone and UN security escorted him away as he waved his finger in their face, saying: "You are here on Egyptian land, don't touch me.
"I asked her a question, she should answer me."
Asked what would happen about her brother's case after COP27 if he is not released, Ms Seif said: "I don't know if my brother will be alive after COP."
Several world leaders have said they have asked the Egyptian authorities, including President Sisi, to let Mr Abd El-Fattah go.
A spokeswoman for the UN's top human rights official, Volker Turk, said on Tuesday he had personally spoken to the authorities to appeal for his release, with the most recent time on Friday.
Mr Turk, the UN high commissioner for human rights, said Mr Abd El-Fattah "is in great danger" and should be "urgently, immediately released".
German Chancellor Olaf Scholz said he raised the prisoner's fate with Mr el-Sissi on Tuesday, adding that "something needs to happen to make a release possible, so that the hunger striker doesn't die".
British Foreign Minister Andrew Mitchell told the Commons on Tuesday Rishi Sunak raised Mr Abd El-Fattah's case in a cabinet meeting and reiterated his commitment to the case.
The PM raised his case earlier with President Sisi at COP27 and "stressed the UK government's deep concern on this issue".
Mr Abd El-Fattah's family has called for him to be deported to the UK to face a court there but his sister said dual nationals are treated as Egyptians by Cairo.
She said if the British embassy is allowed to visit him then he will stop his water strike, which could save his life.
Their mother, Professor Laila Soueif, has been waiting at the gates of Wadi al-Natroun prison for a weekly letter from her son, but it has not appeared.