One shareholder, Debbie Wurzel, has already taken legal action against GM. She is claiming that GM is unfairly favouring a lower bid from News Corp because it involves cash, which GM desperately needs.
GM is worried that other shareholders will follow Wurzel's lead and its advisers have spent the last two days trying to allay investor's concerns about GM's intentions.
Despite these concerns, the chances of News Corp winning out remain high. Analyst Larry Haverty of State Street Research, which owns 1% of the GM division Hughes that owns DirecTV, said yesterday he believed the News Corp deal had a 75% chance of making it.
The complexity of the transaction, which will see News Corp's satellite division Sky Global Networks merge with DirecTV parent Hughes, has intensified because of tough market conditions and the prospect of combining their Latin American pay-TV operations.
News Corp chairman Rupert Murdoch has been negotiating with GM since May after nine months of on-and-off talks. A deal is expected after News Corp's annual results next Thursday.