Sudan's army has called for the UN's special envoy to be thrown out of the country, saying he is "waging war against the armed forces".
Mr Pronk said the army had suffered defeats in Darfur
A military statement said Jan Pronk's presence in Sudan "negatively affects the work of the armed forces".
Mr Pronk wrote on his personal blog last week that heavy losses in Darfur were eroding Sudanese army morale.
Sudan is resisting strong international pressure to allow UN peacekeepers to try and end the conflict in Darfur.
Former armed forces spokesman General Mohammed Beshir Suleiman told the official Suna news agency that Mr Pronk's comments were part of the West's continuing efforts to get Sudan to accept UN troops into Darfur.
"The presence of Jan Pronk in the Sudan constitutes a threat to the Sudan's national security and an immediate decision for his deportation from the Sudan should therefore be taken," he said.
The Sudanese foreign ministry said in a statement that Mr Pronk's remarks were "not in line with his mandate" as a UN representative, but did not repeat the army's call for him to leave.
But the BBC's Jonah Fisher in Khartoum says it may be just a matter of time before Mr Pronk is expelled, after making powerful enemies.
In the statement, the military complained that Mr Pronk had travelled around Sudan without government permission, illegally meeting rebels.
It also accused him of "waging psychological warfare on the armed forces by propagating erroneous information that casts doubts about the capability of the armed forces in maintaining security and defending the country".
Mr Pronk's blog posting last week claimed that Sudan's army had suffered two major military defeats in its campaign against rebels in the western region of Darfur.
He wrote that there had been hundreds of casualties and prisoners taken, leading to a fall in morale and the sacking of generals.
He also said that pro-government Arab militias were again being mobilised in contravention of UN resolutions.
The Janjaweed militias are accused of widespread atrocities, even genocide.
A former Janjaweed fighter now living in London has told the BBC that Sudanese ministers gave express orders for the activities of his unit, which included rape and killing children.
He told the Newsnight programme that Janjaweed fighters would go into Darfur villages after they had been bombed by the air force.
The government has always denied backing the Janjaweed militias and says the problems in Darfur are being exaggerated for political reasons.
More than two million people have fled their homes during the three-year conflict in Darfur.
The UN Security Council has passed a resolution calling for 20,000 troops to be sent to Darfur to replace the 7,000 poorly equipped African Union troops who have failed to end the conflict.
Sudan has rejected the resolution, saying it would infringe on its sovereignty.