However, he was not a man to be taken lightly - as the late dictator Ferdinand Marcos and, more recently, the former president Joseph Estrada found to their cost. In 1986, and again in 2001, the cardinal urged millions of Filipinos to join the revolts which eventually toppled both leaders. His role in the people-power revolution against Marcos was the main act in the life of this highly politicised church leader.

Born into a wealthy provincial family of Chinese parents in New Washington, in the Philippine province of Aklan, Jaime, or "Jim" as he was known, was his mother's pet. The 14th of 16 children, he was a painfully thin, asthmatic child, who often used to cuddle up between his parents to sleep at night. When he asked his nurse why his mother lavished such attention on him, he was told it was because he was the weakest and ugliest of the brood.

From an early age, encouraged by his devout mother, Sin would play at being a priest, giving mock sermons from the living-room table. His mother's last wish was that his siblings look after him, by which time the 12-year-old had already enrolled in the local seminary, St Vincent's.

An ordinary student, Sin's poor health almost prevented him from fulfilling his calling. Laid up in a hospital bed in 1954, he made a pact with himself that if he suffered another asthma attack before the next feast day, he would take it as a sign that God did not require his services. Six months later, aged 25, he was ordained; he never suffered another attack.

After three years as a missionary, Sin became first rector of the St Pius X Seminary in Roxas City (1957-67), before going to Jaro as auxiliary, and later full, bishop. His appointment as Catholic archbishop of Manila in 1974 caused quite a stir; he was, he said, a "small town boy lost in the big city".

Although the Philippines had been under martial law since 1972, the young prelate decided not to judge the regime's exercise in "constitutional authoritarianism". But the honeymoon was short. Within six months, Sin was criticising the authorities after the military raided a Manila seminary on the grounds that it was harbouring insurgents. Official church policy became one of "critical collaboration".

Sin, who, at 47, became the third ever Filipino cardinal in 1976, always felt that Marcos was a man he could negotiate with. He had less time for the dictator's wife Imelda, whose grandiose civic projects appalled him. When she allowed risqué films to be shown under the guise of the Second Manila International Film Festival, Sin declared that "a river of pornography and filth had been let loose on Manila". Imelda retorted that the cardinal was "a communist homosexual".

As reports of the Marcos regime's excesses began to leak out, Sin became increasingly vocal in his criticism. He held regular press conferences to brief the international media, and, as martial law dragged into a second decade, he wondered whether "it is possible we are becoming a nation of sheep".

His answer came after the assassination of the opposition leader and former senator, Benigno Aquino, by Marcos's henchmen in 1983. A stunned public was horrified at the crudeness of the killing - Aquino was gunned down before he even got off the plane on his return from exile - and an exasperated Sin called on the people to take to the "parliament of the streets".

When it became obvious that the snap presidential elections in February 1986 were marred by massive fraud, Sin issued a pastoral letter denouncing the result. He also arranged for vote counters, who had walked out in protest, to hide themselves in a safe house away from Marcos's secret police.

Days later, officers once loyal to Marcos rebelled and holed themselves up inside military headquarters. A band of 300 rebels faced 250,000 Marcos troops. One of their leaders, the former defence minister Juan Ponce Enrile, rang Sin to plead for help, adding that he would be dead in less than an hour.

After much prayer - and despite Vatican opposition - Sin went on the Catholic radio station that evening to ask the people to take to the streets in support of the rebels. Nuns placed their rosaries in front of tanks and people put flowers down the barrels of the soldiers' guns. More than 2m Manilans faced down the military for three days until news spread that Marcos had fled to Hawaii. Not a single shot was fired; Sin called it a miracle.

After Cory Aquino, Benigno's widow, was sworn in as president, the cardinal temporarily distanced himself from politics. He made a second trip to China, the birthplace of his father, and toured the Soviet Union. He also collected an armful of honorary doctorates. A personal friend of Pope John Paul II, he presided over two papal visits to the Philippines.

In most respects, he rigidly adhered to Vatican doctrine - despite his country having one of the highest birth rates in the region, he said that condoms were "only fit for animals". Asked about the population explosion, he responded, "The more the merrier."

Sin was, however, unable to stay away from politics for long. When two of Cory Aquino's successors, Fidel Ramos and Joseph Estrada, tried to amend her constitutional reforms, he attended rallies denouncing the moves.

When Estrada did not respond as Sin wanted, and moves to impeach the populist leader collapsed amid parliamentary shenanigans, in January 2001 the cardinal again joined the military, business leaders and millions of ordinary Filipinos on the streets of Manila. Again, the president was toppled peacefully, and Sin's presence next to the new president, devout Catholic Gloria Macapagal Arroyo, as she took her oath of office could not have sent a clearer signal to the nation.

There was, however, a big difference between the ousting of Marcos and Estrada. The cause this second time was not so clear cut, and Sin laid himself open to accusations that he was not fighting for justice but conspiring with the nation's elite to oust a champion of the poor they could not abide.

His final years were dogged by ill health brought on by diabetes. He retired in 2003. Earlier this year, he was unable to attend the funeral of Pope John Paul II and the ensuing conclave, which upset him enormously. Without a dictator in Manila, he regularly faced charges of interfering in state affairs - to which he responded that it was his duty to praise and criticise governments as the issues warranted.

He will be remembered for his role in the overthrow of Marcos, and for his sense of humour. One of his jokes had him seated between Ferdinand and Imelda. "I felt," he said, "like Jesus ... crucified between two thieves."

· Jaime Lachica Sin, church leader, born August 31 1928; died June 21 2005