Special judge S Natarajan allowed the petitions filed by the Maran brothers and others seeking their discharge, holding that there was no prima facie case against them.
The judge had on March 9 reserved orders for today in the case.
The CBI had alleged that an illegal private telephone exchange was set up at the city residence of Dayanidhi during 2004-06 when he was the telecom minister and it was used for the business transactions involving the Sun Network owned by his brother Kalanithi.
The central agency had alleged that Dayanidhi had caused a loss of Rs 1.78 crore to the exchequer.
Other accused who have been discharged are former BSNL general manager K Brahmanathan, former deputy general manager M P Velusamy, Dayanidhi Maran’s private secretary Gauthaman, and Sun TV officials.
During the hearing of the discharge petitions, the Maran brothers and others argued that they were innocent and did not commit any irregularities as alleged by the prosecution.
Senior counsel Kabil Sibal, who had appeared for the Maran brothers, had contended that the case was foisted on them.