Harmony claimed in a press statement on Monday that Gold Fields head of security, Pine Pienaar, offered a senior Harmony employee a contract to become an informer.
"On November 8 2004, Mr Pienaar specifically requested that the Harmony employee 'collect any documentation lying around about the deal' and he said that 'any information on the take-over bid that you get, I would like to have'," said Harmony.
Gold Field's spokesperson Willie Jacobz said the allegation was untrue.
'Misinformation'
"That is simply not true... it is Harmony misinformation trying to intimidate Gold Fields ahead of its annual general meeting on Tuesday," said Jacobz.
Gold Fields is fighting off a take-over effort by Harmony, which has offered a 29% premium for 100% of Gold Fields' share capital in a two-stage bid.
In the early settlement, Harmony would acquire up to 34.9% of Gold Fields.
Harmony said the deal would provide immediate and long-term shareholder value through sustainable cost savings with a market value of more than R17bn.