"Yemen is in dire need of a political settlement. Otherwise those advocating southern secession will gain the upper hand," Ali Hussein Ashal, a southern politician told Reuters in an interview in Sanaa.
"We do not want Saleh to be toppled in the manner of other Arab leaders, but to initiate reforms and leave peacefully.
"Yemen needs a safe landing and for southerners to feel that they are real partners," Ashal, scion of a political family from the southern Abyan region, said on Friday.
About 10,000 anti-Saleh protesters took to the streets in Aden the same day. Four people were killed and dozens wounded in clashes with security forces. Southerners say the government represses southern protests more violently than northern ones. Ashal is a lawmaker for the Islamist Islah party, part of an opposition coalition that also includes leftists. In the 1960s, his father commanded the armed forces of then-independent south.
"Southerners want an end to the corrupt system, like the north," Ashal declared.
The socialist south merged with the more traditional and conservative north under a 1990 unity deal brokered by Saleh after the collapse of the Soviet Union. Four years later it tried to break away, but Saleh's forces crushed the revolt.
A secessionist movement emerged in 2007 fuelled by perceived northern domination and lack of access to jobs and housing for urban southerners, many of whom are nostalgic about the past when education levels were higher than in the more tribal north.
"Saleh thinks that corruption is a wise way to run Yemen and buying loyalties and distributing privileges will preserve unity," Ashal said, dismissing a presidential offer of dialogue.
"There is no point in entering a dialogue that allows the current regime to reproduce itself and injustices against the south to continue," he added.
Saleh, a northerner who is facing a wave of protests inspired by popular revolts in Tunisia and Egypt, has hinted that Yemen could splinter again without him at the helm.
The south is home to most of Yemen's limited oil and gas resources, but there is no international support for it to break away again. Secession would alarm oil giant Saudi Arabia, which funds Yemen and has long influenced its neighbour's affairs.
Ashal said most southern demonstrators were still sticking to anti-Saleh slogans shared with disgruntled northerners, but argued that southern regional demands must also be met.
He said southerners account for only a sixth of parliament members, although he said they constitute more than 30 percent of Yemen's 23 million people.
Some southern politicians, including exiled former Prime Minister Haidar Abu Bakr al-Attas, have called for federalism, but Ashal said pushing for this now would scare off the north.
Instead, he advocated effective local administration, a fair electoral system and changes to the Yemeni constitution to ensure that southern rights are not trampled.
"Federalism in these circumstances is effectively a first step toward secession," he said. "It can be discussed, but not amid upheaval."