The national broadband network is being connected in Treasurer Wayne Swan's marginal Brisbane seat, only days after a devastating poll for Labor.

Aspley, in Brisbane's north, will be the first site in Queensland's capital to get the optical fibre connection on Wednesday.

A ceremony is being held at the Aspley Rugby League Football Club, just two days after a Nielsen poll showed Labor's primary vote falling to 30 per cent.

It falls on the border of Mr Swan's seat of Lilley, which he holds by a slender 3.2 per cent margin.

Other parts of Aspley fall within the neighbouring marginal seat of Petrie, which Labor holds by 2.51 per cent.

NBN Co said construction had already started on connecting the NBN to other northern Brisbane suburbs.

Several also happen to fall within Mr Swan's seat, and include Nudgee, Virginia, Banyo, Eagle Farm and Northgate.

Brisbane is the fourth capital city to get the NBN.

Melbourne came online in October last year while Hobart and Canberra went live in early February.

It is Queensland's third city to get the NBN, after Townsville and Toowoomba.