Meru and Tharaka Nithi governors and some legislators have rejected the census results.
They have threatened to go to court if 'the figures are not corrected".
Meru Governor Kiraitu Murungi on Monday, through county chief of staff Gideon Kimathi, said the population of the county was higher than what was reflected in the census.
Kimathi, who read a statement on behalf of the governor, said the Kenya National Bureau of Statistics should correct the data or the county administration will seek court arbitration on the matter.
"The Meru population is much higher than this," Kimathi said.
He said the Meru population living in Kina, Ngaremara, Gachiuru, Epiding and other areas bordering Isiolo were enumerated in Isiolo instead of Meru.
He said enumerators at the border were recruited from both counties, hence the duplication of roles.
Tharaka Nithi Governor Muthomi Njuki said the census should be done again in the county, failing which his administration will seek legal redress.
On Tuesday morning MPs from Tharaka Nithi MPs called a press briefing in Nairobi and rejected the census figures.
The MPs included Kareke Mbiuki (Maara), Gitonga Murugara (Tharaka) and Patrick Munene (Chuka Igambang'ombe).
Mbiuki said Tharaka Nithi is known for tyranny of numbers, and they were expecting close to half a million in tally.
"We are calling for a review, or we will go to court to petition the judiciary to annul the census results for Tharaka Nithi," Mbiuki said.
His sentiments were echoed by Murugara and Munene.
Releasing the results at State House Nairobi, KNBS director Zachary Mwangi on Monday said the most populous counties are Nairobi (4.3 million), followed by Kiambu (2.4 million), Nakuru (2.1 million), Kakamega (1.8 million) and Bungoma (1.6 million).
Meru has 1.4 million people and came sixth in the tally.
