GRAIN growers fear they could again be at the "mercy" of Brookfield Rail at the critical time of getting this year's harvest to port when CBH Group's interim rail access agreement runs out on December 31.

Concerns Brookfield could be in a position to exploit CBH's need to get bulk grain to port quickly to fill ships while negotiating on price for a fifth interim access agreement were expressed in two new submissions published by the Economic Regulation Authority (ERA) last week.

A submission by the Wheatbelt Railway Retention Alliance (WRRA) and a private submission by WRRA member and Kondinin grower Lindsay Tuckwell criticised freight rail operator Brookfield's pricing strategies for forcing CBH grain trains from the tracks for 18 hours on May 1.

At that time CBH was attempting to negotiate a fourth interim agreement but declined to sign up to a 25 per cent price increase before the third access agreement ran out.

The next day Brookfield reduced its price increase to 14.5pc in return for CBH guaranteeing to cart certain volumes of grain on rail until December 31.

"It is of great concern that growers and the grains export industry could be forced into a similar situation as at April 30, 2015, with all grower-owned trains (CBH fleet) forced off WA rail lines," the WRRA submission said.

"The possibility of revisiting this situation creates instability, a lack of confidence from customers and marketers, jeopardises shipping slots and the ability to meet customer requirements, thus creating an unnecessary sovereign risk to a vital food commodity to our overseas customers.

"Grain marketers have made it clear that they will not cover the holding costs resulting from slow access to port, any holding costs will be passed on to growers further eroding (their) profitability and viability.

"We have been told by government on many occasions that if growers are not profitable they should not remain in business.

"If Brookfield Rail considers their profits are not sufficient, then they should relinquish the entire WA rail freight network."