Lakeland Dairies has agreed the price for milk for October.
The board said it has agreed a price of 40.25c/L at 3.6% butterfat and 3.3% protein to be paid for October milk in the Republic of Ireland, which is inclusive of the 0.5c/L sustainability incentive payment.
This is a reduction of 4c/L on the price paid in September.
This follows a cut of 3c/L last month.
In Northern Ireland, a price of 32.3p/L will be paid for milk supplied in October which is also inclusive of the sustainability incentive payment.
This is a reduction of 3.5p/L on the price paid in September.
In a statement, Lakeland Dairies said: "Significant market pressure persists as global milk supplies continue to grow from an already strong base.
"Demand is struggling to keep up, which is impacting on butter, cheese and powder returns adding continued pressure on farmgate prices.
"Lakeland Dairies will continue to monitor the markets and will endeavour to support our farmers with the best milk price possible in line with market conditions."
Farmers have been warned in recent days to expect a "bumpy ride" when it comes to milk supplies and global demand.
According to Susie Stannard, lead analyst dairy with the Agricultural and Horticultural Development Board (AHDB), current trends suggest that "milk supplies are running too far ahead of what global demand can absorb".
Stannard said that dairy product inventories are growing globally, "which means that even after production comes under control commodity prices will take some time to recover".
This was well-illustrated in the latest Global Dairy Trade index, which fell for the sixth time in a row last week.