There are also a few experts on here, Cassa!
Firstly I assume you live in England / Wales - not sure of the law elsewhere.
Chris has quoted the legislation, and based on what you say, you and the near neighbours should be able to make an application to the local council to get this route added to the definitive map. This is the map that shows all Public Rights of Way (ROW).
With a ROW, the land on which the path sits is (generally) still physically owned by the landowner, but the public has a right to pass/repass. After 20 years of regular use without formal 'permission', a path can become dedicated as a public ROW. This is afterall how all the footpaths / bridleways in our country came about, centuries ago.
What it will require is a number of local residents to make statemnets that they have been using the path for x years. It isn't necessary for a minimum number of people to show that they persoannly have been using it for 20 years - so you can get an old boy who doesn't get out much these days to declare he used it between 1978 - 1994 say, then others to give different overlapping dates.
You need to talk to the ROW Officer at your local council. Here is some information from N Yorkshire Council on the subject - just as an example for their process. There should be no cost of applying - the council is there to help on this sort of issue. Do it soon, or this newcomer will get away with extinguishing the route.
http://www.northyorks.gov.uk/index.aspx?articl eid=4116