Inaugurating the march called by CPI-M led LDF Opposition, veteran Marxist leader V S Achuthandan said the front would intensify its agitation if Mani did not quit.
Achuthanandan alleged that Chief Minister Oommen Chandy was protecting Mani and had no time for administration.
The Vigilance probe ordered into the case was not going to reveal the truth, he added.
As part of the LDF agitation, marches were held in the districts also.
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The UDF Government a few months ago had ordered closure of all bars, except those attached to five-star hotels as part of its move to take the state to total prohibition in 10 years.
However, the high court permitted hotels in four star and heritage category also to operate bars.
Earlier Government had declined to renew licenses of 418 bars for lack of required facilities.