Adressing an anti-corruption meeting two years after he was elected on a campaign pledge to end corruption, Sirisena said he "regrets" that organised bribery was still prevalent.
"I regret to say that organised bribery and corruption is still taking place in government institutions," he said.
The Sri Lanka president, who has ordered investigations into alleged widespread corruption under his predecessor Mahinda Rajapaksa, said he does not want to take names because those he would name will "go on strike from tomorrow".
"Such is the level of resistance and I am told that officers who refuse to cooperate with organised corruption are sidelined and not given any work by their superiors," he said.
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"We say call tenders to prevent corruption, but in reality we know that the tender procedures are also corrupt. It happens in over 50 per cent of the time. Even the technical evaluation committees are corrupt," Sirisena said.
Sirisena ousted Rajapaksa in January last year, accusing him and his family of corruption. He has also often criticised the national unity government under Prime Minister Ranil Wickremesinghe.
But he was increasingly criticised for failing to allow an investigation of alleged war crimes by the military, while also facing mounting allegations of corruption and nepotism.