The bank's announcement follows Deutsche Bank's disclosure that it had an 8.4 per cent stake in the company and a statement from UBS that it had increased its stake from 8.94 per cent to 10.4 per cent.
The Macquarie-led consortium, Airline Partners Australia (APA), has offered $4.39 per share for the company, which has been rejected by shareholder Balanced Equity Management.
Furthermore, it is rumored that UBS regards APA's bid as undervalued and will also seek a higher price.
The upping of stakes on the part of investors may yet stymie APA's bid, which requires it to attain acceptance from 90 per cent of shareholders, after which point it will be empowered to compulsorily buy remaining shares.
APA currently holds a 30.1 per cent stake in Qantas, with its offer due to expire on April 20th.