Hemasiri Fernando, who was asked by President Maithripala Sirisena to resign, told a parliamentary panel that it was difficult for him to meet Sirisena during the time he served as the top bureaucrat of the ministry.
Sri Lanka's sacked top defence ministry official will face criminal investigation for his alleged failure to prevent the Easter Sunday bombings that killed 258 people and injured over 500, an official said on Monday.
The Attorney General (AG) has instructed the acting police chief to institute criminal action against Fernando following recommendations by a special panel to probe the April 21 attacks.
India had shared intelligence inputs with Sri Lanka about possible attacks weeks before the bombings.
Last week, it was announced that a group of senior police officials were to face criminal negligence charges over their alleged failure to prevent the attacks on the recommendations of the same panel.
The Deputy Inspector General of Police (Colombo), Deputy Inspector General of Police (Western North), Deputy Inspector General of Police (SPR), Senior Superintendent of Police (Negombo), Superintendent of Police (Colombo North), Assistant Superintendent of Police (Negombo III), Assistant Superintendent of Police (Negombo IV), Officer in Charge of the Katana Police Station and Officer in Charge of the Jampettah Police Post were named by the AG in his instructions issued to the acting police chief.
The then police chief Pujith Jayasundera, who was sent on compulsory leave for his alleged negligence, has already moved the Supreme Court against what he termed as illegal dismissal.
Nine suicide bombers carried out a series of devastating blasts that tore through St Anthony's Church in Colombo, St Sebastian's Church in the western coastal town of Negombo and another church in the eastern town of Batticaloa, and three high-end hotels frequented by tourists in the country's deadliest violence since the devastating civil war with the Liberation Tigers of Tamil Eelam (LTTE) ended in 2009.
The Islamic State claimed the attacks, but the government blamed local Islamist extremist group National Thawheed Jamaath for the bombings which killed 258 people, including 11 Indians, and injured nearly 500 others.