On Monday, Speaker Dhanapal disqualifed 18 MlAs owing allegiance to sidelined Deputy General Secretary T.T.V. Dinakaran on the ground they had violated the provisions of the anti-defection law by voluntarily giving up membership of the party (AIADMK) when they gave a memorandum to Governor C.V. Rao against the continuance of Chief Minister K. Palaniswami.