The plans are to create a breathtaking and theatrical enclosure which will become a major leisure and cultural destination.

The scheme will make the Piece Hall the centre-piece of the town's regeneration programme, which is gathering pace with projects including Somerset House, the Shay stadium and the Broad Street leisure and retail centre.

The Courier is backing the bid, which will be put to the Heritage Lottery Fund in September. The whole transformation of the Piece Hall into a vibrant public square could become a £15 million investment with further money to follow from Yorkshire Forward, Calderdale Council and private investors.

Details of the exciting proposals show the historic building housing a centre for creative businesses, upmarket shops and a 4,000-seat amphitheatre. It is hoped work will begin in 2012.

"We want to put in restaurants, bistros and cafe bars, workshops and exhibition space for artists and creative businesses," said the council's community services director Kersten England.

New businesses would go on the top floor and the units on the middle floor would be turned into high quality shops.

"The sort of thing we are talking about is niche, upmarket retailers visitors will travel miles to see. We want to put restaurants and bars on the lower floor, renovating the cellars and creating a new entrance, which English Heritage has said is feasible."

But the biggest change will be to the courtyard which will become a fabulous town square with raked stone seating, a large multi-purpose performance area and a movable stage.

The Piece Hall was built for the sale of cloth pieces in 1779 and restored by the council in 1979. But it has struggled recently to find a useful role.

"We want to provide workshops for artists, crafts people. and 21st century businesses," she said.

The ideas behind this bid have been eagerly awaited and privately some people have said, apart from York Minster, the Piece Hall is the most worthy development in Yorkshire.