Former PQ cabinet minister François Legault said he's leaving politics because he's disheartened over Quebecers' apathy toward politics. (CBC)

Former Parti Québécois cabinet minister François Legault announced Thursday he's leaving politics after 10 years at the national assembly.

Legault said he has lost the motivation to work as a member of the Official Opposition, and has become disheartened over Quebecers' apathy toward politics.

After 10 enjoyable years in public life, Legault said he has found his motivation waning over the last six months, so has decided it was time to step away from politics and find something else to do.

The level of apathy and cynicism he’s seen toward politicians and by the politicians themselves has become a source of deep disappointment, he said.

Legault added he is worried about Quebec's future, saying there is a lot of work to do to raise people's standard of living, to bring public finances under control and to streamline the health and education sectors.

Legault was first elected in his riding of Rousseau in 1998, after a career in business that included the founding and running of Air Transat.

Legault considered running to replace Bernard Landry as leader of the PQ in 2005, but decided against it for family reasons. He served in a number of high-profile cabinet posts including industry, health and education until the PQ's defeat in 2003.

'Very, very bad news' for the PQ

Former Liberal MP and political pundit, Liza Frulla, said Thursday Legault was PQ Leader Pauline Marois's best critic.

Legault had been a thorn in Premier Jean Charest's side over the past few months, hammering the government with questions about the Caisse de dépôt’s $40 billion in losses, and irregularities in the management of Quebec's regional development funds.

Frulla said his departure stood to further weaken the PQ.

"After the end of this week for Pauline Marois, [Legault’s departure] is very, very bad news. She lost the byelection in Rivière-du-Loup … with even a very good candidate," said Frulla. "She’s down in the polls. Jean Charest now is really laughing his way into his holidays."

François Bonnardel, party critic for Action Démocratique du Québec, said the PQ has lost one it its most effective members and has suffered a serious blow, "They lost a big, big, big member of their party. I'm just telling them good luck for the next month and the next years."

Speculation of Legault’s return to politics began even before he officially announced he would be leaving.

"Is he leaving to better come back? Like [Marois] did? Like André Boisclair did? That’s the question," said Frulla.

Legault said he will spend the next year with his family before making any plans about his future.