Police denied permission for the CPF to have its latest rally in front of Yangon's City Hall this week, saying the event would obstruct traffic.
The CPF rallies are in support of The Voice Weekly magazine which in March claimed the Office of the Auditor General had uncovered corruption in six government ministries, including the Ministry of Mines, The Irrawaddy news Web site reported.
Police refusal comes as a court in Yangon's Dagon Township last week said it would decide Sept. 6 whether to proceed with the defamation case against The Voice Weekly by the Ministry of Mines.
The Irrawaddy -- run by expatriate Myanmar journalists operating in Thailand -- reported that more than 30 journalists from local media were present to cover the hearing in Dagon Township. Many of the journalists wore black T-shirts with the words "Stop Killing Press" and black baseball caps with "Press Freedom" on them.
Kyaw Min Swe, editor in chief of The Voice Weekly, said both sides presented final arguments to the court last week.
The journal's lawyer, Win Shwe, said they would fight the case into an appeal if need be.
Immediately after The Voice made its allegations in March, Ministry of Mines officials denied the accusation in the state-run Kyemon newspaper, said a report by the Web site of the Democratic Voice of Burma, a non-profit Myanmar media organization in Oslo, Norway.
DVB said The Voice article cited a report submitted to the Public Accounts Committee by the Union Auditor General's Office. The report said half the shares for a copper mine in the northeast Sagaing region and owned the Ministry of Mines were sold to the military-owned Union of Myanmar Economic Holdings for $100 million.
The payment also was made by a "foreign company" thought to be Chinese owned, DVB reported.
A member of staff at the Voice Weekly told DVB that the publication has substantial evidence to back its claims.
The Voice also claimed the Ministry of Information had pocketed more than $2.5 million when it sold off government newspapers, the DVB reported.
CPF protests and trial of The Voice Weekly come amid the government's latest move to loosen media censorship.
Last week the press censorship board announced that it would end a 50-year-long requirement for pre-publication approval from the Press Scrutiny and Registration Department.
The move was welcomed by many media practitioners but more freedom is needed they said, including abolition of the need to submit their published articles to the PSRD to determine if publishing laws have been broken.
Thiha Saw, the editor of Open News Journal and Myanma Danna magazine, told Irrawaddy last week that some subjects including corruption -- something of which many of the country's top leaders have been accused -- will remain extremely sensitive for the government. Post-publication scrutiny is the PSRD's way of letting editors know the government is watching them.
Incurring the government's wrath could mean the withdrawal of a publication's license to print, a permit mandated under the Printers and Publishers Registration Act.