Ceridian's largest shareholder has hired a financial adviser to look for additional bidders in a proxy battle between the paycheck and human resources company and its activist shareholders.

Pershing Square Capital Management, a hedge fund which has a 15% stake in Ceridian, has hired Lazard to help it pursue alternative offers for Ceridian. It says a $5.3bn (€4bn) cash acquisition bid from private equity firm Thomas H Lee Partners and insurer Fidelity National Financial undervalues the company.