Eskom workers will not be allowed to strike, even if the Commission for Conciliation, Mediation and Arbitration (CCMA) issues a non-resolution certificate, Eskom's human resources head said on Thursday.

Bhabhalazi Bulunga said that the mediation process between Eskom and the three unions representing workers at the power utility - the National Union of Mineworkers (NUM), Solidarity and the National Union of Metalworkers of South Africa (Numsa) - was still ongoing on Thursday.

By late Thursday afternoon they were still in a meeting at the CCMA, attempting to resolve their differences. This followed the issuing of a non-resolution certificate earlier on Thursday.

"Eskom would like to stress that a certificate of non-resolution would not mean that unions could call a protected strike at Eskom, as has been suggested," said Bulunga.

"Eskom has been declared an essential service, and strikes at Eskom are thus prohibited."

He said that the fact that strikes were not allowed was reaffirmed by a High Court interdict obtained by Eskom on May 25.

On Monday evening, Eskom made a wage increase offer of 8%.

The company also offered a 5,6% increase on certain allowances as well as a pay-out of R12 000 to all employees in two equal instalments.

The trade unions rejected the offer and demanded an increase of 9% and a housing allowance of R4 000 per month.

Bulunga said that if a certificate of non-resolution was issued, the next stage in the process for an essential service was that either party could refer the matter to arbitration.

"If a final certificate of non-resolution is issued, Eskom intends to follow that course. An arbitrator, whose decision would be binding on both Eskom and the unions, would then be appointed."

He said Eskom remained hopeful that an agreement could still be reached.