An activist investor has called into question some business moves made by Navios Maritime Partners chief executive Angeliki Frangou.

MRMP-Managers, which holds a 5.8% stake in the boxship owner, has sent a letter directly to Frangou criticising Navios Partners' decision to offer $200m-worth of undervalued shares "at the market" (ATM) while buying $185m-worth of ships at market value.

MRMP argued that the asset value of Navios Partners' fleet of 95 ships is probably worth much more than the New York-listed company's market capitalisation, backed by shares that are undervalued by at least 50%.