Leaders drawn from Tharaka Nithi county have threatened to move to court to challenge the 2019 census results.
Led by Governor Muthomi Njuki, county leaders said the outcome does not reflect what the country knows about it.
They addressed the media on Tuesday in Nairobi.
According to the 2019 census report released on Monday, the county had 393,177 registered people compared to 365,330 captured in the 2009 census report.
Tharaka Nithi was famously thrown into the limelight during the 2007 elections due to its perceived high voter numbers.
In the 2017 general elections, the county had a total of 213,154 registered voters.
Governor Njuki said that the population outcome is important as it reflects the resources to be allocated to the county.
They say the census results is an injustice to the entire area, which needs to be addressed.
Maara MP Kareke Mbiuki said the outcome does not reflect the tyranny of numbers of the county.
“Tharaka Nithi is well known nationally and internationally for its tyranny of numbers. Tharaka Nithi tyranny of numbers was not reflected in the statistics released on Monday,” Mbiuki said.
They said that the preliminary report had estimated the population of the county to be at 480,000 people.
“We are calling upon the Treasury CS and the KNBS to review the statistics which are coming out from Tharaka Nithi county,” the MP said.
The leaders said failure to review the numbers will prompt them to move to the High Court to petition the Judiciary to nullify Tharaka Nithi county's census numbers.
The county's leaders have also asked the KNBS to give a clear explanation on residents of Tharaka-Nithi who were counted outside their county.
According to the report released by the KNBS director-general Zachary Mwangi, Nairobi had the highest number recorded of persons with 4.3 million followed by Kiambu with 2.4 million persons.
The other most populated counties are Nakuru (2.1million), Kakamega (1.8 million) while Bungoma has 1.6 million persons.
Lamu county was the area with the least population captured to be 143,920 persons followed by Isiolo with 268,002, Samburu 310,327, Tana River 315,943 and Taita Taveta which had 340,671.
