A Corby councillor has called for transparency over the land sale that paved the way for the Tesco store in St James industrial estate.
Police are consulting with the Crown Prosecution Service after concluding their investigations into the sale of the plots in 2010.
Corby Council sold the land to developers for £3.8m, but an audit three years later concluded that the land could have been worth up to £13.3m.
And Conservative Cllr David Sims says the people of Corby deserve to know the truth.
He said: “I have spoken to a number of residents and they are all very concerned about this situation.
“In my view this is immoral and illegal and at the end of the day this is a severe issue down to not just one error.
“The local Labour office need to face up and admit to what they have done, nobody has been notified.
“It is in the public interest that the people of Corby find out the truth of what has really happened.
“It’s double standards and I don’t see why they should get away with it.
“Millions of public money that could have been used has been wasted and the people of Corby will be paying for this for a long time to come.”