According to the latest reports, the planned merger between CBS Corporation (NYSE:CBS) and Viacom has been withdrawn by Shari Redstone, who is a vice chair of the board for both companies.

Initially Redstone pressed for the companies to go for a merger, has changed their stance and now supports Viacom CEO Bob Bakish and his plan to bring the company back to dominate. Reports said that Redstone now prefer Viacom to remain an autonomous company, and a letter from her National Amusements is likely to be released shortly.

Both firms reportedly had involved in opening conversations about a deal, but CBS had yet to make a bid for Viacom.

Meanwhile Viacom stock plunged almost 5 percent in pre-market trade.

In the meantime the Redstone family, who possess the majority of voting shares of CBS and Viacom through their privately held National Amusements, had planned re-combining the two media giants almost ten years after they had a split.

Moreover Shari Redstone had mentioned amplified scale as one motive for the merger. Sumner Redstone, National Amusements chairman, divided CBS and Viacom in 2006, considering it would unravel the value of the Viacom side, which had a mob of cable channels regarded as fast growth at time, against CBS Corporation(NYSE:CBS), which held a confronted broadcast network.