Government ownership of a bank, unless government happens to have such a stake purely as a financial investment for return, necessarily has to have the effect of altering the strategies and objectives as well as structure of governance. Government as an owner is accountable to political institutions which may not necessarily be compatible with purely economic incentives.
The mixed ownership brings into sharper focus the divergent objectives of shareholding and the issues of reconciling them, especially when one of the owners is government. In such a situation, one can argue that as long as the private shareholder is aware of the special nature of shareholding, there should be no conflict.