Financially stretched Channel 4 is battling to avoid a further multi-million pound loss as one of the final projects from Film Four, a period epic starring Sir Anthony Hopkins, teeters on the brink of collapse.

Executives at the soon to be closed film unit are understood to have until the end of the week to save Edgardo Mortara, a $20m project about Pope Pius IX that was due to start filming later this month.

Significant sums have been spent designing sets and costumes in Romania and Rome, while it is believed that Sir Anthony could claim a seven figure sum if the project folds.

Although Film Four remains committed to the project, production has run into trouble over financing. Miramax and German firm Senator were co-financing but it is thought Senator has pulled out.

Frantic talks are taking place with potential new backers about ways to save what was set to be Film Four's final high-profile project before closing down.

The only other film it has left in production is the unaffected Motorcycle Diaries, a Che Guevara story.

Negotiations had taken place with The Works, the sales arm of media firm Civilian Content, but are understood to have broken down.

Sir Anthony is due to play Pope Pius IX in the true story of how the Vatican divided Catholics, Protestants and Jews around the world by kidnapping a Jewish boy in 1858. East is East director Damien O'Donnell is set to direct.

Around 50 staff are set to lose their jobs, with the remnants of the business being folded into Channel 4 on a sharply reduced budget.

Film Four and Channel 4 declined to comment.