SIPTU has unveiled plans to demolish Liberty Hall and build a 20-storey building on the site, the top three stories of which will comprise of a heritage centre and sky deck open to the public.

Plans for the union's new headquarters were revealed to delegates at the SIPTU conference in Tralee this afternoon.

The proposed building would have three storeys more than Liberty Hall and would be 24m higher.

It would comprise 15 storeys of office space with a new conference centre and theatre at the base.

The architects say the new structure would be the first commercial building of its kind in Ireland to achieve an A3 energy rating.

The union is not divulging how much the project will cost prior to the tendering process.

General Secretary of SIPTU Joe O'Flynn said the union would be seeking planning permission in the coming weeks and if successful, work could begin in mid 2011.

Three years ago SIPTU announced plans to demolish Liberty Hall which it said was in need of serious renovation.