The largest shareholder in BAE issued a long list of objections to the group's proposed $45 billion merger with EADS on Monday, including concerns over state interference, poor terms and a lack of strategic rationale.
Invesco Perpetual said the deal would also have a negative impact on the British firm's position in the United States, where it has access to sensitive defense work.
"Invesco has, on and off, owned shares in BAE for over twenty years," it said in a statement.
"Invesco believes BAE is a strong business with distinctive positions in the global defense market, especially in the U.S. and UK, and good stand-alone prospects. We look forward to discussions with the board of BAE and other BAE shareholders in the coming days."
It said it owned 13.3 percent of BAE's ordinary share capital.
(Reporting by Kate Holton; editing by Paul Sandle)