The pigeons have nested in some of the city's landmark buildings including the old gasworks, the Telstra tower and some of the city's more gracious, historic bank and government institutions.

Pest controller Grant Morris said that a putrid pigeon infestation so smelly and potentially toxic had caused Bass Labor MHR Jodie Campbell to close her office this week while hundreds of pigeons and their chicks were euthanased and the roof cavity cleared and cleaned.

Ms Campbell confirmed the problem.

"I am continuing discussions with the Department of Finance and Deregulation as a matter of urgency for this problem to be fixed and for my staff to have health assessments and a temporary alternative workplace. The office is currently working remotely as best we can," Ms Campbell said.

Some building owners have spent thousands removing the pests.

The roof of the former ANZ Bank on the corner of St John and Paterson streets was home to hundreds of pigeons and droppings knee deep had to be pumped into a waste disposal truck, Mr Morris said.

"We had to net the whole roof - 25metres by 12metres - and put up bird spikes to keep them away," Mr Morris said.

Mr Morris said it cost from $2000 up to $25,000 to remove pigeons and clean their toxic mess.

He said that he didn't know why the problem had become worse.

"They are worse than rats. You can poison them but the trouble is they tend to drop from the sky. Gas is best to euthanase them," Mr Morris said.

Pigeon fancier and member of the Launceston Pigeon Racing Society Barry Williams said that feral pigeons were the same breed "like homing pigeons gone wild and lost down in City Park".

In Tasmania, "the sky's the limit" with up to $1000 being paid for a top racing pigeon.

But, Mr Williams advised people to block holes in their roofs to stop feral pigeons moving in.

In other Australian cities people are warned not to feed pigeons because of the disease or threat of injury from the very slippery pigeon poo.

The Sydney City Council reports that pigeons spread salmonellosis, aspergillosis, histoplasmosis and the central nervous system and eye disease toxoplasmosis.