MONTREAL—Lino Zambito, the animated businessman who became a star at Quebec’s anti-corruption inquiry, was quietly refused membership in the provincial Liberal Party on Tuesday.

The former construction boss was a household name last October when he became the first witness at the Charbonneau Commission to provide substantive details on the inner workings of a cartel that had worked for over a decade to control infrastructure contracts across the province.

During his testimony, Zambito fingered a number of prominent Liberals and alleged that they had taken illegal campaign contributions.

Days before a debate between Liberal hopefuls looking to replace Jean Charest permanently at the head of the party, the Liberal executive committee voted unanimously to refuse Zambito membership and refund his $5 membership fee.

In a sparsely worded letter sent to Zambito on Jan. 22, party secretary Emilie Nadeau wrote only that Zambito’s memberships had been rejected ”according to the party’s constitution and regulations.” She offered no explanation.

Speaking to the media on Friday, Liberal communications director Michel Rochette explained that Zambito’s “vision of politics does not correspond with ours.”

For a party looking to distance itself from years of contracts tainted by allegations of collusion and corruption, Zambito’s past testimony would be toxic when mixed with the on-stage sparing of leadership front-runner Philippe Couillard and two former Charest cabinet ministers.

Now running a pizzeria north of Montreal, Zambito admitted to giving an influential Liberal organizer $30,000 in campaign funds—an amount far exceeding provincial limits.