April 12 (Reuters) - Pendal Group Ltd said on Tuesday the A$2.40 billion ($1.78 billion) non-binding takeover offer from asset manager Perpetual Ltd "significantly undervalued" the Australian investment manager.

The A$6.23 per share offer for Pendal, a former unit of Westpac Banking Corp, was first disclosed on April 4 and was at a 39.2% premium to the stock's close on April 1.

Pendal said that after assessing Perpetual's cash-and-stock proposal, it has determined that the offer was not in the best interests of its shareholders.

Perpetual did not immediately respond to a Reuters request for comment. ($1 = A$1.35) (Reporting by Harish Sridharan and Savyata Mishra in Bengaluru; Editing by Maju Samuel)