Chris Mutangadura, the state prosecutor, said: "Although the judge has dismissed our application .. on the grounds that our chances of success are slim ... we will be filing to the Supreme Court against that decision.
"... If the Supreme Court also dismisses our application, then that is the end of the road."
Bennett's detention had raised doubts about the sustainability of the new unity government formed last month after almost a year of political turmoil.
The new government has Robert Mugabe, Zimbabwe's president since 1980, sharing power with MDC's Morgan Tsvangirai, sworn in as the prime minister last month.
Bennett had initially been charged with treason but the charges were quickly replaced with accusations that he allegedly plotted to buy weapons to attack a telecommunications station in Bromley, east of the capital, Harare.
Bennett denies the charges against him and faces up to life in jail if convicted.
Tsvangirai sworn in
Three weeks after becoming the prime minister, Tsvangirai was sworn in as a member of parliament on Tuesday.
The new PM is expected to lay out his priorities for the new government in his first official speech on Wednesday.
Zimbabwe has come under ever worsening economic and health crises amid the political divisions that led to the formation of the unity government.