Mala was the officer who initially busted Lageri for associating with Turaga at Deep Sea Night Club last year.
The letter encourages Bainimarama to bring in the officers involved, including Naivalurura, saying 'I have faith in you to clean up the Fiji Police Force.'
Fiji police and customs have been waging war with drug racketeers in recent years with Nadi International a popular destination for drugs destined for New Zealand and Australia, or coming in to the country.
In 2010, authorities also busted a drug ring involving several foreign nationals handling narcotics at an estimated value of $28FJD million (NZ19.8 million dollars) with police saying they had also confiscated a large amount of white powder believed to be raw material for a drug product and allegedly originated from China.
Weeks before, border protection agents at Nadi International Airport had also seized close to 15,000 pills of Contact NT - used to manufacture crystal methamphetamine.
In August last year, Custom officers found a large consignment of marijuana or Indian hemp at Nadi. It had come in from New Zealand.
An insider says a senior official in Bainimarama's office knew about the drug ring allegedly involving Naivalurua, Brown and Lageri but did not tell him about it.
Bainimarama has been away in India and Manila but returned late this week. Sources say the letter exposing the January drug consignment and implicating Fiji's top police officers has been on his desk waiting for him.
The letter has also been sent to the Minister of Defence Minister, Joketani Cokanasiga.
Page one of the letter
Page two of the letter