Small business truck owners protested outside Eskom on Friday, saying it had reneged on coal transport agreements in favour of big companies.

"We are supposed to be getting paid on tonnage. Eskom has reduced our tonnage, thereby rendering our businesses almost insolvent," said Teboho Joala, chairman of the Coal Transporters' Forum.

About 100 truck owners protested outside the Eskom headquarters at Megawatt Park in Sunninghill, Johannesburg.

Joala said the contracted coal movers ? all small and black-owned businesses ? had bought the trucks based on the contracts they signed with Eskom from 2004 onwards.

But problems started escalating in September last year, when bigger companies started getting most of the work.

"People are going bankrupt, getting liquidated, blacklisted, all because Eskom are not honouring our contracts. All the time we've been negotiating with Eskom, and they have been making proposals which we have accepted, but Eskom is not sticking to its word," said a protester who did not want to be named.

Eskom spokesman Fani Zulu could not immediately be reached for comment.