MILAN, March 28 (Reuters) - Italian market watchdog Consob has ruled out that any of the three slates of nominees filed for the board of Monte dei Paschi di Siena (MPS) could be deemed illegitimate, a person with direct knowledge of the matter said.

The person said Consob, in close consultation with the European Central Bank, had dismissed a complaint filed by MPS's board on Thursday regarding a slate submitted by small investor PLT Holding intended to hand CEO Luigi Lovaglio another mandate.

The source said Consob was keen to dispel any residual doubts given the wording of an MPS statement on Friday which spoke of "preliminary" interactions with authorities.

MPS's statement said that, based on these preliminary contacts and information received so far, all the slates of board candidates were legitimate.

Instead, Consob's position is final, the source stressed.

The regulator wants investors to have full clarity on the matter, given that governance advisers are working on the voting recommendations they will give to shareholders ahead of the April 15 vote to elect a new board and CEO at the bank.

PLT has challenged the slate filed by the MPS board, which is trying to unseat Lovaglio and replace him with Fabrizio Palermo, currently the CEO of utility Acea.

A third slate has been filed by fund manager association Assogestioni.