The offices in Cathays Park, Cardiff, are home to government staff
Nearly £42m could be spent refurbishing Welsh Assembly Government headquarters in Cardiff, BBC Wales has learned.
Detailed plans are being drawn up to refit the offices in Cathays Park, the Dragon's Eye programme has discovered.
First Minister Rhodri Morgan has indicated his support and a project team is working on the plans at a cost of £100,000.
But Welsh Conservative leader Nick Bourne called the idea "astonishing" when public bodies are facing cuts.
The assembly government said the accommodation was inflexible and unable to respond to changing business needs.
The public image is diminished, according to the government, and there are health and safety issues.
But Mr Bourne accused the assembly government of feathering its own nest.
"On the one hand they are calling on councils and public bodies to tighten their belts yet on the other are more than happy to spend huge amounts of public money on refurbishing their own HQ and filling it with new desks and chairs," he said.
Kirsty Williams, leader of the Welsh Liberal Democrats, said the assembly government needed to get its priorities right.
"It's absolutely shocking that the Labour-Plaid government can justify spending this amount of money on refurbishing their offices," she said.
The assembly government inherited its headquarters from the Welsh Office [now the Wales Office] at the time the Welsh assembly was created in 1999.
It consists of two buildings, the first built just before World War II and a much larger extension completed in 1980.
The buildings are the main location for assembly government staff.
An Assembly Government spokesman said many parts of the building were reaching the end of their economic life and investment would make the building more environmentally sustainable.
Refurbishment would also reduce the assembly government's use of external conference facilities, he said.
"This project is at the very initial stage and will be subject to the development of a sound business case before any investment decision is made," added the spokesman.
Dragon's Eye is on BBC One Wales on Thursday at 2235 GMT.