Sarkozy said in a statement to AFP that he was resigning "immediately" from the Constitutional Council to "regain his freedom of speech" to react to the decision by the council.
France's top constitutional body had earlier confirmed that the ex-president had gone beyond spending limits during last year's election campaign and would lose out on a 10-million-euro ($13-million) reimbursement.
The Constitutional Council said in a statement that it was confirming a decision by France's electoral finance watchdog that Sarkozy had filed expenses of nearly 23 million euros, which exceeded the spending ceiling by 2.1 percent.
Because of this Sarkozy, who lost to Socialist Francois Hollande in the vote, is not eligible for the reimbursement of 47.5 percent of total campaign spending he was due under election financing laws.
Sarkozy will also need to return 150,000 euros advanced by the state for the campaign.
The former president has been implicated in a series of campaign funding scandals allegedly involving Liliane Bettencourt, France's richest woman, and former Libyan dictator Moamer Kadhafi. Sarkozy has denied any wrongdoing.