The actor played the role of British businessman Harry Bright, who is floated as the possible father of Amanda Seyfried’s Sophie Sheridan-Rymand.
Speaking to Sky News, Firth revealed that he was unable to provide any solid details on whether a third Mamma Mia film would or would not go ahead.
However, he said that he was keen to return to the franchise, adding the rest of the cast – which includes Meryl Streep, Pierce Brosnan, Dame Julie Walters and Dominic Cooper – would also be up for reprising their roles.
“We can always dream,” he said. “I'm sure that you won't find anybody that wouldn't be keen to show up for it.”
“The likelihood of [a third Mamma Mia film] I can't comment on, you know,” he added.
The first Mamma Mia! was released in 2008, and was based on the 1998 stage musical set to the music of Swedish pop hitmakers Abba.
While many of the band’s best-loved songs have already featured in the first two Mamma Mia! films (some of them twice), Firth suggested that there was still more mileage to be found in them.
“I suppose there are more songs,” he said. “Or why not use them all again?”