BANGKOK — The Thai government faced a political uproar on Wednesday after details surfaced of a proposed prisoner amnesty that the country’s opposition says is designed to pardon Thaksin Shinawatra, the prime minister ousted in the 2006 military coup.

Thai officials did not provide details of the proposed amnesty, saying it was secret and needed approval from more than a dozen government committees before it could become law. But the prospect of an amnesty for Mr. Thaksin, who remains an extremely divisive figure in the country, stunned and angered opponents of the government — now headed by his sister — and risked aggravating old wounds.

The government already faces major discontent over the handling of the country’s worst flooding in decades. The authorities tried to protect the economy and the capital, Bangkok, channeling waters away from industrial sites and parts of the city but often increasing the damage to the rural areas that form Mr. Thaksin’s main support base.

The prisoner amnesty issue has reinforced resentments. “It’s so obvious that this was done specifically for Thaksin,” said Abhisit Vejjajiva, the leader of the parliamentary opposition. “Please stop,” Mr. Abhisit advised the government. “This will create disharmony.” He criticized the government for raising the issue “during a time when people are suffering,” referring to the flooding in Bangkok and surrounding areas.