Israeli Prime Minister Ariel Sharon
Israeli Prime Minister Ariel Sharon yawns during a session of the Israeli parliament in Jerusalem October 20, 2004.Reuters

The condition of former Israeli Prime Minister Ariel Sharon has worsened with his vital organs failing, according to the director of the hospital where he has been treated for eight years.

Zeev Rotstein of Tel Hashomer hospital said that the team has seen "a gradual decline in the functioning of Ariel Sharon's vital organs which are essential for his survival".

He added that Sharon's condition is "critical" and his "life is in danger". The family of the 85-year-old Israeli politician is at his bedside.

Sharon has been in a coma since 2006, when a shattering stroke incapacitated him five years after being elected prime minister.

The former military general and hardline right-winger has been suffering from renal failure in recent days but could not undergo dialysis due to the dangers of the procedure for his weakened body.

"He has not undergone dialysis," Rotstein said. "He is still getting the same medical treatments he has been getting for years."

"If there was a problem in just one organ, it would be a different story, but [Sharon] is suffering problems in a number of organs."

Sharon has been getting medical care and receiving fluids through a feeding tube. Last September, a surgery corrected a problem in his intravenous feeding system.

In January, MRI scans showed that Sharon's brain was significantly active, as it responded to various stimuli such as family pictures, a recording of his son's voice and human touch.

Known for his bold tactics, Sharon fought in all of Israel's wars since its founding in 1948. In both the 1967 and 1973 wars, he led a division that played a key role in Israeli victories.

After he became defence minister, Sharon masterminded the controversial invasion of Lebanon in 1982 after the shelling of Israel by the Palestine Liberation Organisation.

During the invasion, Lebanese Christian militiamen allied to Israel exterminated hundreds of Palestinians in two Beirut refugee camps under Israeli control.

An Israeli commission of inquiry ruled that Sharon – known by locals as the "Butcher of Beirut" – had a personal involvement in war crimes committed by Israeli soldiers.

He was elected prime minster in February 2001, months after walking through Jerusalem's al-Aqsa compound, an action that sparked the second Palestinian intifada.

Although a promoter of the construction of Jewish settlements in the occupied Palestinian territories in the West Bank, Sharon ordered the unilateral withdrawal of Israeli troops and settlers from the Gaza Strip in 2005. The move is believed to have boosted the rise of Islamist militant Hamas group in the area.

Sharon also commenced the construction of the controversial West Bank barrier, known as the Wall, in response to a wave of attacks by Palestinian militants.

In 2005, he left the right-wing Likud Party to establish the centrist Kadima Party. After the stroke, his deputy Ehud Olmert took over and was elected prime minister.