Sanaa, Yemen (CNN) -- Ali Abdullah Saleh is no longer Yemen's president, but he is still wielding political clout as the head of the ruling party.
Saleh has threatened to withdraw all members of his party from the national government and warned the prime minister he could face imprisonment.
Protesters took to the streets in mass demonstrations over the past year, calling for Saleh's departure from office. He finally stepped down last month in exchange for immunity in part of a power transfer deal brokered by the six-nation Gulf Cooperation Council.
However, he remains president of the ruling General People's Congress party.
Tension has escalated between Saleh and the new regime after new President Abdu Rabu Mansour Hadi said he was planning major reforms, said Yahya al-Arasi, Hadi's spokesman.
Prime Minister Mohammed Saleh Basendowah recently attended a ceremony at Change Square in Sanaa and condemned the old regime's attacks against unarmed youth protesters. The square was the base of the protests that erupted last year against Saleh's rule.
As a result, Saleh threatened to imprison Basendowah if he does not listen to his orders, a presidential aide who asked not to be named because of the sensitive nature of the issue.
"Saleh informed the prime minister to take orders from him or else he will take him to prison," the aide said. "Saleh has not yet realized that he is not president and such actions will turn the country into chaos. Saleh must leave the country if the international community seeks to see a stable Yemen."
Saleh threatened to withdraw all members of his party from the national government to protest the way Hadi's administration is dealing with the political crisis in the country, embroiled in discord and violence.
"The former president is complicating matters and making it difficult for factions to go forward with reforms in Yemen," al-Arasi said.
Hadi has taken precautionary measures, his spokesman said. He will announce the formation of a new unity government if Saleh orders his party officials to step down from their posts.
Senior GPC officials told CNN that Saleh was angered at the president and prime minister's stances.
"Both men are trying to damage the image of the GPC leader. Saleh is still the president of the largest party in the country and must be treated with respect," said a senior GPC aide who asked to remain anonymous.
But opposition parties condemned Saleh's verbal attacks on the prime minister. They called on Hadi to stand against Saleh and what they say are his efforts to ruin the country after he was forced out of power.
Mohammed Qahtan, a senior opposition Joint Meeting Parties official, said it's sad that Saleh's GPC officials are remaining quiet about Saleh's maneuverings.
"We regret the fact that Saleh threatens the prime minister and his party leaders are quiet. The GPC have to choose between joining the government under President Hadi or standing with a person who lost all legitimacy to power in Yemen," Qahtan said.