Macquarie Group and Credit Suisse have given the strongest signal yet that the proposed $1.2 billion merger of Mantra Group and French giant Accor is likely to proceed, after snapping up millions of shares in the ASX-listed Australian hotel and resort operator on behalf of subsidiaries and global and local investors.

Ahead of a key decision later this week by the Australian Competition and Consumer Commission (ACCC), the Macquarie platform surged up the Mantra register, acquiring about eight million Mantra shares on February 27 to become a substantial shareholder with 5.2 per cent stake.