Sir Philip Green has set his lawyers against Frank Field over claims the Labour MP made his £363m BHS settlement.
Field spearheaded the parliamentary inquiry into the collapse of BHS, and, in a radio interview last week, said he had received a "major leak" of information relating to Green's contribution to the BHS pension scheme.
BHS shut its doors last year after Green sold the chain to serial bankrupt Dominic Chappell for £1. A parliamentary inquiry branded Green the "unacceptable face of capitalism" for his role in the scandal.
In a letter to Field, Green said: "I sadly find myself forced to write to you following a disgraceful radio interview you gave last week making yet further allegations about me.
"You seem intent on continuing your personal and bitter attacks on me, making allegations, in my view, wholly without substance. You claim you have new dynamite evidence against me. How can this be the case when the document you referred to on the radio is not new; it is a document produced by the regulator last year?"
The retail tycoon's lawyers have now contacted Field in a letter that Green said he should read "very very carefully".