The former Arsenal, Celtic and West Ham striker has also revealed he once owed over £300,000 to bookmakers, as well as banks and friends he had borrowed money from to feed his addiction.
Hartson, who has recovered from testicular cancer, said: "Some people just can't let it go and they are still hassling me.
"They are still offering me the opportunity to bet, trying to make a way into my friendship," Hartson told The Sun.
"I don't want to go down that road again. I've paid back as much as I can of my debts. I cannot physically afford to pay any more."
Hartson has seen his pension taken away to pay off creditors and has also entered into an Individual Voluntary Agreement to repay 12p in the pound of his remaining debts.
Harston added: "At one point I owed between three and four hundred grand.
"I have done my best to pay back what I can because I have never knocked anyone in my life.
"I'm a good guy, I was struggling with an illness - gambling."