"The board's stated operational and financial plan strikes us as being inadequate and underwhelming given the substantial opportunity thoroughly detailed by Pershing Square," Glass Lewis said in a report issued this week.

The voting will occur on November 7.

Ackman has followed a variety of tactics in challenging the ADP leadership. He has proposed expanding the ADP board, extending the nomination deadline so his Pershing Square Management could field five candidates, along the current challenge to three incumbents.

The proxy fight has gotten contentious with ADP claiming Ackman's candidates are not qualified and that Ackman and his allies have not suggested anything the company has not already considered.

In a prepared statement, ADP said, "Glass Lewis fails to recognize ADP's outstanding track record of outperformance relative to our peers and the broader market, the strategic investments ADP has made to develop new, innovative technology and services, and the stewardship and strength of our Board."