Proposals for the Pentland Film Studio in Straiton were called in by the Scottish Government more than a year ago after Midlothian Council failed to make a ruling.
Backers have previously warned the subsequent delay threatens to put £140 million of investment at risk.
The Scottish Government”s planning and appeals division submitted a report to ministers the end of last month.
Scottish Tory culture spokesman Jackson Carlaw has now written to Culture Secretary Fiona Hyslop asking for asking for clarification on it future.
Mr Carlaw said: “Now that decision”s apparently in, it needs to be revealed immediately.
“It would be utterly wasteful to wait any longer.”
Film and television producers spent a record £52.7 million shooting in Scotland last year.
Recent shoots include Macbeth, starring Michael Fassbender, and Victor Frankenstein, starring James McAvoy and Daniel Radcliffe.
Outlander, the television series based on the novels by Diana Gabaldon, is filming for a third series in Scotland.
But critics have warned the country has repeatedly lost out to Northern Ireland and Wales.
Wales has 51,000 sq ft of purpose built studio space and Northern Ireland has 42,000 sq ft – but Scotland can only offer 5,800 sq ft.
The 96-acre Pentland site would include a water stage along with six sound stages.
Last year the Association of Film and Television Practitioners Scotland warned First Minister Nicola Sturgeon that failure to back the plan will jeopardise the industry north of the Border.
Green MSPs have opposed the studio amid claims it would result in the eviction of Jim Telfer, 82, a tenant farmer.
Nick Gibsone, whose family own the land at Damhead, Midlothian, have denied the claims.
The Scottish Government said final submissions were not made to its planning and appeals division until November with an independent reporter submitting their recommendations on December 22.
A spokesman added: “Ministers will publish their decision as soon as the report has been fully considered.”