Malcolm Cardinal Ranjith said there must be thorough questioning as to how the bombings took place on April 21 and who helped the attackers.
Nine suicide bombers belonging to local Islamist extremist group National Thawheed Jamaat (NTJ) linked to ISIS carried out a series of devastating blasts that tore through three churches and as many luxury hotels on the Easter Sunday, killing 258 people, including 11 Indians.
"I will not hesitate to hit the streets to safeguard the rights of our people", Ranjith told reporters at a religious event at Ragama in north Colombo.
The Cardinal said that although he was happy with the ongoing presidential probe launched by President Gotabaya Rajapaksa''s predecessor Maithripala Sirisena, yet he saw a process that lacked transparency.
"I can sense that some of the things which need to come out are being hidden – who was responsible?, who aided them and kept contact with them (the jihadi group)?," he asked.
"There must be questioning from the highest to the very lowest level," he said.
In February, the Sri Lankan government appointed a six-member team to help police collect authentic information and expedite an ongoing presidential probe into the devastating attack.
President Rajapaksa decided to "speed up the ongoing investigation into the attack which had proved crucial in his decisive electoral victory last November.
Rajapaksa used the Easter Sunday terrorist attack to portray himself as the leader who could stop terrorism.
The voters gave him a big mandate and elected him as President in November last year. Rajapaksa stormed to victory, trouncing his nearest rival Sajith Premadasa by a margin of over 13 lakh votes - 52.25 per cent of votes polled against 41.99 per cent.
The previous government headed by Maithripala Sirisena and Ranil Wickremesinghe was blamed for its inability to prevent the attacks despite the prior intelligence made available on the impending attack.
Rajapaksa, who pledged an independent probe, continued with the same panel appointed by Sirisena. PTI CORR MRJ MRJ