Elstree Studios is in talks with financial backers over plans to raise £10m to build a third large stage within two years, taking the total number of stages to eight.
Under the expansion plan, which dates back to August last year, a 30,000 sq ft stage will bebuilt on wasteland at the Borehamwood facility.
Elstree Studios managing director Roger Morris said it had been turning away work for more than a year because of a lack of capacity.
He said: “If we had a stage that big, we would be able to fill it all the time, across TV and film work. When you build a new facility, you have to be aware of overpricing and not build it as a dream - we have to make sure that what we build is right for the marketplace.”
Morris said he hoped to build the studio “within 24 months”.