Canadian firm Potash Corp has scored the apparent tactics of BHP Billiton Ltd to spread 'doubt and confusion' about the company's future following the giant resource firm's hostile bid for the world's largest manufacturer of fertiliser.

Potash rejected the proposal and in a letter addressed to the company's customers and dated August 30, it revealed that BHP's marketing director Chris Ryder started 'to cold call them', which the company characterised as "inappropriate and highly unethical form of contact."

The fertiliser company said that it was forced to conclude that BHP Billiton intends to create unnecessary concerns on Potash Corp's future when it raised questions "about our ability to do business across the nutrient spectrum as well as the future location and makeup of our sales organisation."

Potash stressed that such move from a reputable company like BHP was totally disappointing and any attempt to undermine the fertiliser maker's determined effort to serve its clients were uncalled for.

Potash Corp formally rejected the billion-dollar proposal by BHP last week, describing the hostile bid as 'wholly inadequate' while revealing at the same time that the company is currently considering offers from other suitors.