POPULATION forecasts used to pressure Kyogle Council into merging with its neighbours has been labelled a "statistical aberration" in NSW Parliament.
Upper House Labor MP Peter Primrose said the data used to support the government's Fit for the Future modelling was flawed from the get-go.
"Academic studies on the accuracy of future population projections in local government areas have repeatedly found that there is not a particularly high level of accuracy," he said.
"In the case of local government areas in mining regions, with large indigenous populations or with small populations, the accuracy was particularly poor.
"Yet such long-term population forecasts were precisely the deciding factor in the controversial scale and capacity criteria used to assess whether councils were Fit for the Future.
"Making such critical policy assessments based on broad-based demographic projections so far into the future is simply not a sound basis for policy."
Mr Primrose quoted author Mark Twain, whose autobiography shed light on his own feelings about statistics.
"Figures often beguile me, particularly when I have the arranging of them myself, in which case the remark attributed to Disraeli would often apply with justice and force: 'There are three kinds of lies: lies, damned lies and statistics'," he quoted.
Population projections had continually proven to be wide of the mark even in Australia, Mr Primrose added.
"In the 1980s and early 1990s, for instance, everyone knew that the suburbs of inner Sydney would continue to decline in population because this was simply a continuation of the long-term trend," he said.
"Well, that historically based projection did not quite work out, Mr Premier."
Sydney's population was about 3.2 million in 1980 and is tipped to reach five million within a year.
Kyogle Mayor Danielle Mulholland has said her council would not submit a voluntary amalgamation request by the government's looming cut-off date of Wednesday.