The Australian Competition and Consumer Commission will investigate the near-simultaneous 6c per litre milk price rise announced in Brisbane by Parmalat (Paul’s) and Dairy Farmers on Thursday.

"The ACCC has already written to the companies seeking reasons behind the price rise and the fact that one company’s rise was almost immediately followed by a similar rise by the other," ACCC Chairman, Professor Allan Fels, said.

"The ACCC will investigate if there was any collusion in the price increase.

"It will examine all the circumstances surrounding the price rise"