British milk production hit another 25-year high last month, according to an industry survey of daily milk deliveries.
The amount of milk delivered to dairies in November totalled 1,009m litres, AHDB's new provisional figures show.
This figure is 2 percent above last year and the highest November volume since 1995.
As a result of disruption to markets this year, AHDB said a number of farmers moved milk buyer recently, and this had 'thrown out estimates of milk deliveries'.
Chris Gooderham, AHDB Dairy's Head of Market Specialists said: "Over the last 2 months, these movements have meant the coverage in our weekly milk production survey has increased from 76.3% to 77.6% of total production in GB.
"While at first glance that might not seem like a significant change, in reality it would alter the estimate for the whole of GB by some 18m litres per month.
"While we had factored in an increase in the weighting because of those movements, the latest data suggests we underestimated the changes that took effect from 1st October.
"The latest re-weighting puts GB milk deliveries in October at 1,025m litres, 0.6% above October last year."
He said the solution to further improving the accuracy of estimates was for more companies to get involved in AHDB's weekly milk deliveries survey.
"By doing so, our coverage will increase, limiting the risk of farmers moving from a company outside the survey to one within it, or vice-versa.
"If you are a milk buyer and would like to discuss how you can get involved, please get in contact," Mr Gooderham said.