The siblings of Singaporean Prime Minister Lee Hsien Loong on Wednesday accused him of abusing his position and said they had lost confidence in him as head of the city-state.

Lee Wei Ling and Lee Hsien Yang said in a statement published on their Facebook accounts that they felt "threatened" by their older brother's "misuse of his position and influence over the Singaporean government and its agencies to drive his personal agenda", reports Efe news.

They added that they feared "the use of the organs of state against us" and that Hsien Yang felt compelled to leave the country.

The siblings also accused Hsien Loong's wife Ho Ching of meddling in government affairs, promoting their son Li Hongyi's political career and expressed concern over the country's lack of measures to prevent the abuse of power.

In the six-page letter, the two siblings also criticized the Prime Minister's refusal to follow the terms of the will of their father Lee Kuan Yew, the founder of modern Singapore who died in 2015, regarding his private residence.

Kuan Yew said in his will that he wished the house to be demolished, but Wei Ling and Hsien Yang accused Hsien Loong of using his position to disregard his father's last wishes in an attempt to "milk" his legacy to boost his popularity.

"The values of Lee Kuan Yew are being eroded by his own son. Our father placed our country and his people first, not his personal or private agendas," the siblings said.

"We feel hugely uncomfortable and closely monitored in our own country. We do not trust Hsien Loong as a brother or a leader. We have lost confidence in him."

The Prime Minister expressed sadness over his siblings' letter and denied the accusations, arguing that sibling differences should remain within the family.

"Since my father's passing in March 2015, as the eldest son I have tried my best to resolve the issues among us within the family, out of respect for our parents," Hsien Loong said, as reported in The Straits Times.

He added that his siblings' statement had hurt their father's legacy.

The family row emerged last year on the first anniversary of their father's death when the Prime Minister's sister Wei Ling accused Hsien Loong of abusing his power and attempting to create a political dynasty.

Hsien Loong assumed office for the second time after the 2015 general elections, which he convened six months early after the death of Kuan Yew.

The People's Action Party, founded by Kuan Yew, has governed the country since its independence.

In the 2015 election, the party won its best result in years following a campaign in which Hsien Loong linked his governance to his father's legacy.

Criticism of the government is unusual in Singapore, a country with one of the highest per capita income in the world but where the media is subject to strict censorship.