Ms Ho Ching, the wife of Prime Minister Lee Hsien Loong, had no right to loan documents belonging to the late Mr Lee Kuan Yew to the National Heritage Board (NHB) for an exhibition, said Mr Lee Hsien Yang.
In a Facebook post yesterday, the younger brother of PM Lee again accused his sister-in-law of interfering with the late founding prime minister's estate, and also took issue with the NHB over the matter. His latest missive followed Ms Ho's account last Friday of how she came to be involved in the loan.
She said she had found the items while tidying the late Mr Lee's house in April 2015, the month after he died, and had been told of their significance by PM Lee.
PM Lee then suggested loaning the items to NHB for an exhibition on his late father's life, and Ms Ho arranged for it through the Prime Minister's Office (PMO), all the while keeping the siblings informed and emphasising that the items belonged to the estate and must be returned.
Yesterday, Mr Lee Hsien Yang said he and his sister, Dr Lee Wei Ling - joint executors of their late father's estate - had never authorised Ms Ho to remove the items.
"Informing the executors after the fact does not give her the right to intermeddle," he said.
Ms Ho had been dragged into the dispute between her husband and his siblings over the late Mr Lee's Oxley Road house, after Mr Lee Hsien Yang charged that she had taken their father's belongings without permission.
Mr Lee Hsien Yang yesterday also said the PMO was in no position to loan to the NHB the late Mr Lee's personal items, saying they did not belong to the PMO.
He said: "We again note that the estate's residual items fall under the executors of our father's estate... not the beneficiaries or the PMO."
He said neither Ms Ho nor PM Lee were named as executors in "any of the seven drafts" of the late Mr Lee's will.
He added: "Ho Ching somehow believes that acting on behalf of the 'PMO' gives her licence to take LKY's (Lee Kuan Yew's) personal belongings and interfere with the estate... This oversteps the legal rights of the PMO."
He also questioned how she could "act on behalf of PMO, despite having no official position in PMO".
The items were documents, including a telegram sent by the late Mr Lee in 1958.
Mr Lee Hsien Yang said he and Dr Lee did not object in principle to the loan of their father's items to the NHB and had, in fact, given away many of his belongings to the NHB for another exhibition about Singapore's pioneer leaders.
But he charged that the NHB tried to return them "after 'someone senior' ordered them to unwind the gift", referring to an alleged attempt not to proceed with part of the exhibition.
National Development Minister Lawrence Wong, who was in charge of the Ministry of Culture, Community and Youth when the exhibition was held, said in a Facebook statement last Friday that Dr Lee and Mr Lee Hsien Yang had imposed "several unusual conditions" for the use of the items.
He said these included a request to prominently display the first part of a demolition clause from Mr Lee's will - which calls for the house to be demolished after Mr Lee's death or when Dr Lee moves out - but to leave out the second part, which states that if the house cannot be demolished because of any change in government rules, then it should be open only to his family and their descendants.
But Mr Wong said his ministry eventually decided not to pursue the matter and let the NHB proceed with the exhibition, which is still on.