A partially burnt-out vehicle and a gas canister are among the items left littering a site just off one of the main roads into Kettering.
The Northants Telegraph reported last November that a number of Travellers had parked up on Cransley Park just off the A43 and A14 near Kettering.
Several caravans were moved onto the site, which has been awaiting development for 10 years, and have remained there for about two months.
The Travellers have recently left the site, but the area has been left strewn with rubbish, including clothing, bedding, a bike and a gas canister.
There is also an abandoned vehicle which looks to have been partially burnt-out.
A spokesman for the Countywide Traveller Unit, a single body that manages unauthorised encapments and Gypsy and Traveller-related issues on behalf of local authorities, said back in November that it is private land so their role was just to give advice to the landowner.
Cransley Park is owned by the St Francis Group, a UK-based property development and investment group.
The Northants Telegraph contacted the group for a comment on the site and the condition it has been left in, but is yet to have a response.
Plans to build a business park including offices and a hotel on the former Cransley Iron Works site were first submitted in 2006.
Revised plans then went in last year to increase the number of warehouses at the site, which were approved, but there does not appear to have been any movement on the development since then.