A fly infestation will force the evacuation of two ministerial offices today.



Level 19 of Bowen House will be swept and fumigated from midday, forcing Attorney General Chris Finlayson, Revenue Minister Peter Dunne and around 15 staff out.



It's understood the bugs are vinegar flies and the problem became obvious earlier in the week in Finlayson's office and spread through the suites.



''We are not full of flies, although there a few pesky ones about,'' a source said. ''Good excuse to head off early for the weekend.''



It's not the first time a building in the Parliamentary complex has been emptied because of flies. In May 2010 a suspicious package prompted a full evacuation of the Beehive.



It turned out to be a box of cluster flies. A note was found on a box in cabinet minister David Carter's office, saying it contained a bomb.



An infestation of flies could come from rotting fruit or blocked drains.



Flies can carry diseases such as dysentery, gastroenteritis and E.coli and can transmit intestinal worms.



Warning signs of a infestation are clusters of the insects - dead or alive, tiny spots of droppings usually found on pipes or light fittings, or maggots.

A spokeswoman for Parliamentary Service said: ''As you would expect with office buildings there are general maintenance issues that come up from time to time and recently we were made aware of a potential fly incursion within an office in Bowen House. This is being dealt with as part of routine maintenance.''