“If you look carefully at the statements made by the government and the police in particular… You’ll see an utter lack of seriousness on the government’s response on the issue at hand,” privately-owned Daily Nation newspaper quoted him as saying.
Mr Dewji, reportedly Africa’s youngest billionaire, was taken by masked gunmen in the Tanzanian city of Dar es Salaam on Thursday last week.
The abduction took place outside a swanky gym in the affluent neighbourhood of Oysterbay.
The kidnappers fired shots in the air before driving away with the billionaire, eyewitnesses said.
His family has offered a 1bn Tanzania shilling ($440,000; £330,000) reward for information that leads to his rescue.
Mr Dewji, locally known as Mo, is credited with turning his family business from a wholesale and retail enterprise into a pan-African conglomerate.
His company, MeTL, has interests in textile manufacturing, flour milling, beverages and edible oils in at least six African states.
Meanwhile police have released 19 of 26 people who were arrested in connection to the abduction, The Citizen newspaper reports.