Australian investment manager AMP Capital has sold a 15% stake in itself to Japan's largest financial company, in a bid to secure a cornerstone investor ahead of a push into the world's second-largest savings market.

Mitsubishi UFJ Financial Group will pay A$425m for the stake in AMP parent company AMP Capital Holdings, according to a statement. A representative from trust bank subsidiary Mitsubishi UFJ Trust and Banking will also take a seat on AMP's board.