Radical plans to transform Bradford's City Hall could rip out its historic Council chamber and replace it with a winter gardens complex open to the public.

A new chamber created out of Yorkshire Stone and glass could also be built in Centenary Square as part of a major re-design of the area.

Leeds architects Bauman Lyons, who drew up the ideas, were picked as the winners of a Designs on Democracy competition aimed at making local authority buildings more accessible to the public.

A processional promenade - flanked by stone columns - is envisaged to link the 'new' chamber to City Hall and the new building would be heated by solar panels on the roof.

Solar energy would also be used to power a massive public media screen, under the plans.

Now the plans for the grade one star-listed building have been passed to Bradford Council and will be the subject of massive public consultation.

But even the architects have admitted the ideas may never see the light of day.

Councillors, officers and English Heritage will also be in intensive talks about the plans for City Hall which is recognised as one of the finest buildings in Britain.

The architects, who designed the unusual bus shelters on Manchester Road with heated seats and wind turbines, beat other top British architects to win the competition organised by the Institute for Public Policy Research, the Commission for Architecture, the Built Environment, Architects Journal and Design Council.

The Designs on Democracy competition was to make Britain's city and town halls more accessible to local people and also saw similar plans for Stockport in Cheshire and Letchworth, Hertfordshire.

Bauman Lyons believe the panelled Council chamber is under-used, inaccessible and represents the grandeur and values of another era.

The winner's preferred option is to remove the whole core of the building, including the Council chamber, and replace it with winter gardens extending into Centenary Square, public spaces and attractive courtyards. There would be cafes, restaurants and exhibitions in huge areas now used for storage as well as dusty out-of-date offices.

The pavilion in Centenary Square would be built to last just 25 years, a recognition that democracy and society are changing at an unpredictable rate.

A second option by Bauman Lyons keeps the Council chamber and creates a museum trail opening up City Hall's unseen treasures. The plans for leisure, open spaces and courtyards would remain the same.

Ben Rogers, senior research fellow for the Institute of Public Policy Research, said: "Town halls are the public face of local councils. Yet most are forbidding and neglected. I think the plans for Bradford are wonderful and would put the city on the map. The designs now are the property of Bradford Council and it is up to them to decide what to do. There will obviously be some intensive talks."

But Bradford's Lord Mayor, Councillor Richard Wightman, warned there were important hurdles to overcome before there could be any changes to the 132-year-old landmark.

He said the people of Bradford, officers, councillors and organisations must have their say. Coun Wightman also said no alterations could be made without the consent of conservation watchdog English Heritage.

Irene Bauman Lyons, practice managing director, said: "We are absolutely delighted, but we don't want to impose anything on people. We want to save existing features which are sensitive and valued by people."

Deputy Council leader Councillor Simon Cooke said: "We need to challenge the purpose and function of City Hall in the 21st Century and make it more accessible to the public.

"This magnificent old building defines the city, but most people in Bradford have never even been inside it, which is a great shame. We want to work with the architects to encourage people to use it and enjoy it without detracting from its splendour.

"Some see City Hall as an impenetrable rock, but we already have the tourist information office, the Hear to Help(correct) office on the ground floor and people getting married in the former court room and Council chamber.

"There is no reason why we couldn't open other parts of the building.

"Personally I wouldn't want to see the Council chamber go. It is part of the Grade One Star listing but it is good for us to be challenged this way."

He said the ideas would provide a valuable spring board to create a City Hall which the public could enjoy, but stressed no decisions had yet been taken.

If a scheme was adopted funding would be sought from the lottery and public and private sector, said Coun Cooke.

But today leader of the Council's Labour group, Councillor Ian Greenwood, said: "It would be civic vandalism of the worst kind. I am not in favour of it and think it is outrageous such changes should even be considered.

"City Hall is one of the wonders of architecture and it should be all about the use of the building rather than changing it."

Leader of the Council's Liberal Democrat group, Councillor Jeanette Sunderland, said: "We need good functional, modern offices from which we can provide good services to the public.

"But it is essential that any changes should not be done in isolation and should take place together with the regeneration of the city centre. I do think the public should be encouraged to make use of City Hall."

Bradford City Hall was chosen by the competition by the organisers because of the bid to become European Capital of Culture in 2008 and measures the Council had already taken to encourage people to visit the building.