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, al-Arasi said.