Three Greenpeace activists, two dressed as cows, have been arrested during a protest at the Melbourne headquarters of milk giant Murray Goulburn.

They were calling on the company to support the extension of the moratorium on genetically engineered food crops and to stop GE contamination of its Devondale dairy products.

Greenpeace GE campaigner Louise Sales said the three protesters were arrested inside the Murray Goulburn premises, but later released.

Ms Sales said Murray Goulburn claimed its products were GE-free, but the company wanted the GE food crop bans lifted.

"Genetically engineered food could already be creeping into our milk because their dairy herds are allowed to be fed on up to 5 per cent GE feed."

She said Greenpeace's attempts to talk with Murray Goulburn chief executive Stephen O'Rourke had met with no success.

"The response has been hostile - we've tried repeatedly to meet with him and other executives at Murray Goulburn."

Ms Sales said if GE food crop bans were lifted, Australian dairy farmers would have no choice but to accept GE feedstock and Australia would lose its lucrative GE-free status.

"When GE crops were introduced in Canada, widespread contamination followed and segregation proved impossible."

Once released into the environment, GE crops cannot be contained and will lead to the inevitable contamination of our fields and our food, Ms Sales said.

Comment was being sought from Mr O'Rourke.

AAP