Phosphate company Legend International Holdings will spend over $20 million to acquire all the shares it does not own in North Australian Diamonds (NAD) through an on-market takeover.

The Joe Gutnick-led Legend said it has instructed brokerage Aequs Securities to spend 1.2 cents on each of the 1.7 billion NAD shares that are offered to it between now and May 26.

Shares in East Perth-based NAD climbed 0.2 cents to 1.3 cents at 14:04 AEST.

Legend already holds a 34.04 per cent interest in NAD.

In October last year, Mr Gutnick was appointed executive chairman and managing director of NAD.

Legend primarily holds phosphate projects in Queensland while North Australian's flagship project is the Merlin diamond project in the Northern Territory.