Achuthanandan's admission comes two days after the CPI(M) Central Committee censured him for defying the official line on these issues and also at the direction of the party to openly admit the mistakes.
"I acknowledge the organisational fault on my part as self-criticism and accept the disciplinary action taken by the party on the Kudanmkulam power plant issue," Achuthanandan, who turns 89 later this week, told reporters here.
Achuthanandan, a former Chief Minister, had also come under attack for deviating from the party's line at the CPI(M)'s two-day state committee meeting that ended yesterday.
"I agree that it was an organisational mistake on my part to make an attempt to visit the KNNP to pledge support to the people agitating against the plant at time when the party had taken a stand in favour of the Indo-Russian project," he said.
Achuthanandan said it was also a fault on his part to have compared State Party Secretary and his bete noire Pinarayi Vijayan to S A Dange, who presided over the split in the undivided CPI in 1964.
Achuthanandan, who is the Opposition leader in the Assembly, has been censured by the party Central Committee twice in last three months, first over the "Dange" remark and then on the Kudankulam issue.
On the issue of murder of T P Chandrasekheran who had floated his own outfit Revolutionary Marxist Party after being removed from CPI(M), he said it was a mistake that he visited the house of the slain leader at Onjiayam in Kozhikode on the day of Neyattinkara assembly by-poll, where the CPI-M led LDF candidate lost in March last.