ADP laid out what is said is series of fluctuating statements by Ackman and Pershing on a number of issues, claims detailed in aeptember 21 investor presentation. This included Ackman's position on the company's leadership.

Starting with an approach on August 1 with CEO Carlos Rodriquez, Ackman expressed" lack of confidence in the executive. ADP says the position shifted through a series of succeeding communications: "Work together if shared vision"; "Willingness to work with Rodriguez; "Suggests CEO Change" and finally on September 17 "Willinesness to Work with Rodriguez."

ADP also claimed Pershing significantly misrepresented the size of its ownership in ADP. Pershing asserts it has an 8.3-percent stake. However, ADP says the total is really 2 percent with Pershing's figures including 28 million unexercised call options on shares the investment firm cannot vote.

Meanwhile, Ackman's firm dismissed the September presentation as not representing a clear response to Pershing's position and said management's plan will not deliver claimed margin expansion.

Pershing also fired back at some of ADP's claims about qualifications of directions. "The directors we seek to replace do not have technology or industry expertise, a criticism ADP has leveled at our Nominees, and include a business school dean, and two former industrial sector CEOs," Pershing wrote this week

Originally Pershing nominated three candidates, but then asked ADP to extended the nomination process so it could nominate five, which would have represented a majority. More recently, Ackman suggested ADP add three seats on the board to accommodate Pershing's nominees.