Fred M'membe was Tuesday ordered to report at police headquarters for an "interview" amid an ongoing public row in which senior government officials have accused The Post of "trying to run the country".
M'membe, in editorials published in recent weeks, has criticised the government of President Levy Mwanawasa on a number of fronts, including the government's failure to stem corruption and its poor delivery track record.
He has called on the leader to resign and persistently questioned his commitment to "honest public service" and his will to stamp out corruption in light of several unresolved cases involving government officials.
M'membe's views have sparked a call by ruling party supporters for a ban on The Post, the only private daily newspaper in the nation of nearly 11 million people.
The country's justice minister George Kunda has condemned the newspaper for "trying to run the country" and forment "anarchy".
In an editorial published Tuesday, The Post noted: "Levy Mwanawasa and his minions have lost what little credibility they ever had in the eyes of fair-minded Zambians. Many people detested and strongly disapproved of the way Levy came to power. The arrogance and pomposity that has characterised his presidency has disappointed many".
But the newspaper added that regardless of this, "many people were prepared to give him a chance".
The government's approach to free speech in Zambia has become an issue of concern for local journalists, church groups and international media watchdogs.
Reacting to the case involving M'membe, the Council of Churches in Zambia on Wednesday warned that the government would fail to protect and safeguard peace unless it allowed freedoms of speech and expression.
Regular public debates around free speech are held in the capital Lusaka. At one such gathering, titled "The media clampdown: Is it a sign of an emerging dictatorship in Zambia?" on Sunday, robust debate on individual cases in which journalists were called to answer to government came under the spotlight.
Journalists began campaigning for reforms to the country's media laws in 1993, but to date, laws that allow journalists to be questioned and harassed remain on the statute books. Recently a journalist from the popular radio Phoenix station was dismissed for reading out a letter sent in by a listener with strong views against the government.
Senior Zambian journalist Kellys Kaunda speaking at a meeting about the need for media reforms, arranged by the local chapter of the Media Institute of Southern Africa, warned: "We do not want to survive on the goodwill of people in office because these offices may not always be occupied by good men".
The apparent strong arm approach of the government towards the media has been put down by some observers to the fact that Zambia is a democracy with huge developmental and image challenges under Mwanawasa, who is widely seen as a "minority president" with feelings of insecurity given that he came to power with less than 40 per cent of the vote.