An internal investigation is under way into the exact payment method used to share out an €11m milk price top-up to Kerry milk suppliers.

The Irish Farmers Journal understands a calculation error resulted in the wrong payment to some suppliers.

For the first time, the “leading milk price” top-up was paid on a milk solids basis rather than a volume basis.

It is understood both Kerry Group and Kerry Co-op agreed this was the right thing to do.

Last week, a text message to suppliers suggested an 0.85c/l bonus was on the way.

Some suppliers were disgruntled, angry and perplexed when it turned out to be over 1c/l for some and 0.6c/l for others.