Harin Fernando, minister of telecommunications, said a letter had been sent out warning of the attack. According to the Mirror, Mr Fernando shared the letter on Twitter, which he said had been “ignored”. Sri Lanka’s deputy inspector general of police had signed off the letter on April 11, less than two weeks before the series of explosions tore through churches and hotels.
At least 200 people died in Sunday’s attacks, leaving a further 450 injured.
The letter said that a plan to target Catholic churches and the Indian High Commission in the country’s capital Colombo had been uncovered.
The note claims members of the National Thawheeth Jamaath Islamic group were behind the attacks.
Mr Fernando tweeted an image of the letter, adding: “Some intelligence officers were aware of this incidence.
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“Therefore there was a delay in action. What my father heard was also from an intelligence officer.
“Serious action needs to be taken as to why this warning was ignored. I was in Badulla last night.”
Sri Lankan prime minister Ranil Wickremesinghe said he had been made aware of the plans but that officials had not kept him up to date.
He made it clear an investigation was needed into the attack but said the first priority would be to find that attackers.
Seven arrests have reportedly been made.
Furious social media users condemned Sri Lankan authorities after reading the letter.
One said: “So you’re telling us, as a member of parliament, your own father told you of this last night, which is why nobody you loved died, but you and the rest of your buddies who actually knew let the rest of us just die?
“I’m having a real hard time understanding this.”