Lancaster Grand Theatre has launched a £1m campaign which will transform the 230-year-old building.
Plans have been submitted to Lancaster City Council for a glass-fronted two-storey foyer to the side of the theatre, facing on to the existing car parks.
It will feature a new box office, bar, exhibition and performance space and will provide access to the existing foyer, leading into the theatre itself.
Lancaster Footlights, the charity that owns the theatre, which was built in 1782 and is the third oldest in the country outside London, said it had already raised £160,000 and was now looking for significant backers to hit the £1m target.
Mike Hardy, chairman of Footlights, said the development “would take the theatre forwards into a new era”.
The new plans come after a previous application granted in 2008 had expired.
Mr Hardy said: “Centros were going to pay for it at part of the big plans for the canal corridor, but it doesn’t seem to be making much progress.
So we’ve decided to do it ourselves.
“The foyer has been redesigned, it’s slightly bigger, but it’s got practical features which will be an advantage, including more usable space in the foyer itself.
“There will also be a disabled hoist to the bottom of the circle inside the theatre, and a spiral staircase to the left of the foyer, instead of the steps at the back of it.
“It solves a lot of issues that we have at the moment and it will allow us to have a much bigger reception area and gives us much more circulation space.”
Mr Hardy said it would also provide a small space for theatrical workshops, and performances for artists.
He added: “It will make The Grand capable of providing conference facilities because we’ll finally be able to provide catering.
“It will take the theatre into a new era.
“We’ve already raised £160,000 ourselves which is largely down to the goodwill of Lancastrians, and the total cost is just over £1m.
“The plan now is to get planning permission and then go out to try to attract some of the larger funding organisations and see how successful we are.
“We’ll just have to see how we get on, but we’re very optimistic.”