The fields, either side of junction 3 at Rothwell, were purchased for what is believed to be £110,000 in 2016 and the council paid surveyors to assess the site.
They remained tight-lipped about any future plans for the site, which was bought without scrutiny from backbench councillors, and three-and-a-half years later the land remains empty with no plans for future use.
A Kettering Council spokesman said: "The land in question was bought as a long-term strategic land holding. That remains the case."
Opposition leader Cllr Mick Scrimshaw (Lab) said he is worried the council will "take the easy option" and continue to sit on it.
He said: "They bought that land at the time as a commercial investment but did not know what they were going to do with it and have been sitting on it.
"That money has effectively been wasted. I think it was a really bad decision.
"To spend public money you should know what you are going to do with it and know what the return is going to be. To spend it without knowing that is absolutely ridiculous."
He added that there should be a review of what the land could be used for and that if there if there is found to be no public benefit the land could be sold to recoup the money.
Independent councillor Jim Hakewill believes the land would make a "wonderful" country park for Rothwell and that people in the town should be asked what they want it to be used for.
He said: "No commercial business would buy land and do nothing with it and have no idea what they are going to do with it.
"The best thing would probably be to hand it over to Rothwell Town Council who may have the vision to do something with it."
The buying of commercial properties and land by councils as an investment is not uncommon, although some commentators say such deals are akin to gambling public money on the property market.
In recent years Kettering Council has also bought an office block in Yorkshire for £5.2m as well as the iconic RCI building in Kettering Parkway for £4.35m.
Council documents show about one third of the council's £1.5m in additional income in 2019/20 came from commercial investments.