June 10 (Reuters) - Australia's Boral Ltd said on Thursday an independent expert's estimate valued its shares as much as 40% higher than suitor Seven Group Holdings Ltd's off-market takeover bid price, and asked shareholders to reject the offer.

Seven, whose interests range from industrial services to media companies, had offered in May to buy all the shares it does not already own in the construction materials maker for A$6.50 apiece.

The independent expert concluded that the offer by Seven Group, which had come without a premium, was neither fair nor reasonable, Boral said, adding that the expert estimated its fair market value to be between A$8.25 and A$9.13 per share.

The offer by billionaire Kerry Stokes-owned Seven Group comes on the heels of a stellar rally in Boral's shares this year, underpinned by a hot property market and after Seven failed to increase its stake in the company to 30%.

Seven Group currently owns a 23.18% stake in Boral.

(Reporting by Vasudha Kaukuntla in Bengaluru; editing by Uttaresh.V)