A "political vehicle" is needed to challenge the ANC's dominance, Democratic Alliance leader Helen Zille has said.

"Any country that is governed by the same party for longer than 20 years is setting itself up for serious abuse of power," she told the party's Mpumalanga Congress on Saturday, according to a copy of her speech issued on Sunday.

The only "guarantee against a slide into irreversible power abuse" was the periodic transfer of power between competing political visions and forces.

"It does not help service delivery if voters support a government, en masse, and three months later are on the street protesting against poor service delivery. They must realise that they change their governments through their vote, not the toyi-toyi."

This is why she was calling for a "realignment of opposition parties" to create a vehicle to challenge the ANC at the polls.

She warned that the only way such a political force could be created was if opposition leaders had their egos in check.

"South Africa needs opposition leaders who are big on vision and courage but small on ego pride; leaders who will seize the day, and who will put the country ahead of their own status. I believe the leaders of the most significant opposition parties in SA today embody these very characteristics," she said.