Pretty much not. It's also probably against the tree presevation order in your area, but check with your local council to be sure. What sort of tree is it?
You can prune roots, but probably not the size that you're talking about. Roots grow partly in an opportunistic way in search of water, and partly in response to the loads created by the tree. Urban trees have larger wider spreading roots than forest trees (even of the same species) because urban trees grow wider and in isolation so they see more wind forces. The short end of the stick is that if you cut the roots, the tree will probably fall over. Not straight away, but perhaps a few years later when you get the right combination of rain softening soil, and winds.
I did a removal job on a tree just last week in bondi near sydney. A contractor had dug out the roots of a fairly large eucalyptus tree while developing a property. There were big winds here last week, and it toppled the tree. The area is full of units, the tree knocked out 3 fences, 4 clothes lines, pancaked 2 cars, a satellite dish and a shed. The council is taking the contractor to the land and environment court. If precedent is anything to go by he's facing a minimum $100k fine plus damages.
Shaun
