The C.L.A.S.S.E. student federation voted this morning against Charest's proposal to stretch the tuition increase over seven years instead of five.
Two other major student groups are still debating the offer.
Meanwhile, the Quebec Liberals decided to move a party convention next weekend from Montreal to quieter Victoriaville to try to avoid protesting students.
Earlier this month protesters managed to get into a convention centre in Montreal, leading to a showdown with riot police.
They delayed Charest from giving a speech for about an hour.
More protests are scheduled in Montreal and across the province today.
Charest's offer made Friday hasn't done much to quell the unrest.
On Saturday evening, thousands again marched through Montreal to denounce the planned $1,625 increase in tuition, weaving through downtown streets and jamming up traffic.
The demonstration was smaller and tamer than a night earlier, though, with no arrests or major incidents.
As the dispute approaches its 12th week, about a third of Quebec students are still avoiding classes, but most have chosen to return to school.
In addition to drawing out the increases over seven years, Charest's offer would also bolster the loans-and-bursaries program, while tying future tuition increases to the rate of inflation.
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