Prime Minister Lee Hsien Loong has raised doubts over parts of his father's will

A feud between the children of Singapore's late founding leader intensified Wednesday after two siblings publicly accused their brother Prime Minister Lee Hsien Loong of disobeying their father's last wishes and abusing his powers.

Singapore's founder Lee Kuan Yew is largely credited with transforming the city-state from a relatively poor British colony into one of the world’s wealthiest and most stable societies.

His eldest son Hsien Loong became Singapore's third prime minister in 2004, taking over the People's Action Party (PAP) which has governed Singapore since it gained self-rule in 1959.

"We have felt threatened by Hsien Loong’s misuse of his position and influence over the Singapore government and its agencies to drive his personal agenda," read a statement posted online by younger brother Hsien Yang and younger sister Wei Ling.

It was an extraordinary public criticism of the city-state's top leadership in a country where tough laws against protests and curbs on press freedom have stifled political dissent.

The siblings' grievances largely centre on the fate of the family's home after their father's death.

The Lee patriarch, who died two years ago, warned against building a personality cult around his legacy and feared his old bungalow would be turned into a museum if it was not demolished.

The pair said their brother Lee had defied their father's instructions to tear down the house.

- 'Absurd claim' -

"We have observed that Hsien Loong and (his wife) Ho Ching want to milk Lee Kuan Yew’s legacy for their own political purposes," the statement said, adding that they harbour political ambitions for one of their sons.

Ho, a former civil servant, is the chief executive of state investment agency Temasek Holdings.

The prime minister, who is on vacation overseas, fired back with his own statement, saying he was "deeply saddened by the unfortunate allegations".

"Ho Ching and I deny these allegations, especially the absurd claim that I have political ambitions for my son," Lee said.

"Since my father’s passing in March 2015, as the eldest son I have tried my best to resolve the issues among us... out of respect for our parents," he added. "My siblings’ statement has hurt our father's legacy."

The premier's siblings also alleged they were being closely monitored, adding they had lost faith in their brother's ability to lead.

"We feel hugely uncomfortable and closely monitored in our own country," they said.

"We do not trust Hsien Loong as a brother or as a leader. We have lost confidence in him."

Hsien Yang, a former brigadier-general like his brother, added that he "will leave Singapore for the foreseeable future" over the widening rift.

He is currently chairman of the Civil Aviation Authority of Singapore after holding top jobs in Singapore Telecom and beverage giant Fraser & Neave.

Wei Ling, a medical doctor, is senior adviser to the National Neuroscience Institute.

- Rare public criticism -

The public dispute involving the country's first family has gone viral online in a country where open criticism of the ruling party is rare.

Lee Kuan Yew, despite his major achievements in bringing economic prosperity, was criticised by rights groups for restricting political freedoms, including muzzling the press, jailing political opponents and suing critics for defamation.

Premier Lee and former prime minister Goh Chok Tong have also sued critics for defamation.

The junior Lee led the PAP to a landslide victory in the 2015 general election, six months after the death of his father sparked a massive outpouring of support for the former leader's legacy.

Analysts said that despite the quarrel, Lee's political position was unlikely to be affected.

"Lee Hsien Loong I don't think will be challenged politically, his position is quite secure," Michael Barr, associate professor of international relations at Flinders University in Adelaide, told AFP.

But he said the question remains whether this incident would affect "Brand Lee".

Political analyst and former nominated lawmaker Eugene Tan said the dispute puts Lee in the "challenging position of having to defend himself while at the same time ensuring that confidence in Singapore’s government remains unshaken".