Mr Lee Hsien Yang and Dr Lee Wei Ling's concerns over the ministerial committee that they have attacked appear to have been triggered by its questions on their late father's will, Senior Minister of State for Law Indranee Rajah said yesterday.

In a series of pointed questions to the younger Lee siblings, she asked: "Why are they so concerned?"

The Lee siblings accused the ministerial committee studying options on Mr Lee Kuan Yew's Oxley Road house of doing the bidding of their brother, Prime Minister Lee Hsien Loong, to block the house from being demolished.

But yesterday, Ms Indranee and other MPs in Parliament said they were unclear over what the dispute was really about.

She questioned why Mr Lee Hsien Yang disputed the existence of the ministerial committee.

Ms Indranee pointed out that both he and Deputy Prime Minister Teo Chee Hean, who chairs the committee, held the same position - that they did not want the house to be completely preserved.

Nor did they want it to be redeveloped into a commercial site.

"If that is the case and if (Mr Lee Hsien Yang) is saying exactly the same thing as DPM Teo, where is the dispute?" said Ms Indranee.

Given that both parties agree that the extreme options are out, there was nothing wrong with studying other options for the Oxley Road house, she added. "Nothing has been decided. How can studying these options be an abuse (of power)?" asked Ms Indranee.

The junior minister went on to say that the Lee siblings' concerns appeared to have been triggered by the committee's questions on the late Mr Lee's will.

In a statement a fortnight ago, PM Lee publicly raised concerns over the circumstances in which his father's final will was made.

He asked what role his sister-in- law Lee Suet Fern and her law firm played, and whether they had a conflict of interest, as her husband Lee Hsien Yang was a beneficiary of the estate. The sixth will had given Dr Lee an extra share, but the last will reverted to the original equal division.

Ms Indranee said that under Singapore's laws, the lawyer drafting a will is required to be independent.

Quoting a 2009 Court of Appeal judgment in the case of Low Ah Cheow and Others v Ng Hock Guan, she said: "The preparation of a will involves serious professional responsibilities which solicitors must uncompromisingly observe and discharge."

The issue was not whether the late Mr Lee knew what he was signing, but "whether he received independent advice as the law uncompromisingly requires", she said.

She noted that the late Mr Lee had consistently taken independent legal advice for his lawsuits and his first six wills.

But it is not for the committee to decide whose claim on how the will was drafted is valid, as it is simply trying to understand Mr Lee's wishes on the house, she said.

Other MPs also directed questions at the two siblings about the circumstances of Mr Lee's will.

Ms Lee Bee Wah (Nee Soon GRC) asked who actually drafted the late Mr Lee's final will, pointing out Mr Lee Hsien Yang said his cousin Kwa Kim Li did. But Ms Kwa denied doing so.

Ms Sun Xueling (Pasir Ris-Punggol GRC) noted that since their statement on June 14, "there has been no clarification by the siblings on who drafted the last will and the circumstances in which it was prepared".

Ms Indranee said that the younger Lee siblings "have made plenty of allegations, but we have not seen any substance and no evidence".

She added: "(Workers' Party chief) Mr Low (Thia Khiang) himself had said the siblings provided no evidence.

"And to me that is most significant, that these allegations are just that - allegations."