Talking to reporters here, Karthikeyan said he had already conveyed his decision to Chief Minister Oommen Chandy, KPCC president V M Sudheeran and senior leader A K Antony.
He said he would tender his resignation once the party leadership accepted his request.
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Two days' ago Karthikeyan had met Sudheeran, who is now on a foreign tour, to make it clear that he was keen to quit as Speaker on conclusion of the monsoon session of the House yesterday.
The move has also triggered speculation of a reshuffle of the Congress nominees in the UDF ministry with Karthikeyan getting accommodated in the cabinet with an important portfolio.
However, Chandy or Sudheeran have so far refrained from making any commitment in this regard.