PANAMA CITY (Reuters) -Canadian miner First Quantum's contract to operate a lucrative copper mine in Panama is unconstitutional, Panama's Supreme Court declared on Tuesday following weeks of protests against the deal.

Challenges against the company's new contract, which was approved on Oct. 20, piled up in court amid public anger over the deal, which opponents regard as too generous.

"We have decided to unanimously declare unconstitutional the entire law 406 of October 20, 2023," said Supreme Court President Maria Eugenia Lopez.

The contested contract gave First Quantum a 20-year mining right with an option to extend for another 20 years, in return for $375 million in annual revenue to Panama.

The company did not immediately reply to a request for comment.

Demonstrators have argued the contract terms are too generous to First Quantum and allege corrupt practices in its approval. The company denies this.

In response to the protests, Panama's government enacted a bill in November banning all new mining concessions and extensions.

(Reporting by Elida MorenoAdditional reporting by Valentine Hilaire and Natalia Siniawski)