Federal Labor have attacked the NSW government for deliberately holding back details of a damning state Ombudsman's report before a key vote on the Murray-Darling Basin Plan.

The NSW Ombudsman on Thursday made an unprecedented correction, tabling a report that criticised the WaterNSW - a state agency - for providing figures on compliance action over water that "was incorrect to a significant degree".

The Darling River has suffered from excessive upstream irrigation, pastoralists such as Rob McBride says. Credit:Louis Douvis

The Ombudsman published a report last November based on WaterNSW data that claimed 117 penalty notices or prosecutions over a 16-month period when in fact there were none.

The watchdog had been alerted to the errors by former and current staff and informed NSW Regional Water Minister Niall Blair on February 12.