Twenty livestock farmers have been ordered to appear in court on fraud charges after they were caught fiddling their books about how many cows were on their farms.

More than 100 other farmers have been fined between €700 to almost €24,000 for fraud over cattle numbers, the public prosecution department said on Monday.

The fraud, involving farmers claiming they had fewer dairy cows than they actually had, first came to light in early 2018. By registering multiple calves to the same mother, they were able to pretend that the real mother had not yet calved, so did not produce milk.

Cows which have not yet calved are considered 50% less polluting in terms of phosphates, and farms could therefore keep more animals and remain within official limits. Some farmers were even able to claim subsidies because it appeared on paper as if they had reduced the size of their herds.

When the scandal broke in early 2018, farm minister Carola Schoten banned 2,100 farms from selling their herds or moving their animals to new locations while the fraud was investigated.

The public prosecution department has now concluded dozens of farms were involved in fraud and that they had a combined 3,000 more cows than they should have had. On some farms, the fraud involved more than 100 calves.

Half the 125 farms which face legal action and fines had deliberately fiddled their books, the department said. The rest had made genuine mistakes, but were fined because their livestock administration was a mess.

Investigators used DNA checks to trace which calves belonged to which mother.