Michael Spencer, via the IPGL (Holdings) Limited vehicle which owns 16.8% of Deltic, does not intend to support the unsolicited takeover offer, according to a letter received by the company.
In the letter, Spencer meanwhile reiterated its continuing support of Deltic's management team.
Spencer detailed that the Reabold offer does not place an appropriate value on Deltic and “lacks any compelling strategic rationale, commercial logic or sufficient operational synergies.”
He adds that the offer “does not reflect the commercial and technical risks associated with the Reabold portfolio and their potentially dilutive impact on Deltic's own portfolio and prospects.”
Deltic last week rejected the proposed share-based takeover offer which, at 1.5 Reabold shares per Deltic share, was pitched at £12.3mln or 0.87p per share.
In a subsequent note, SP Angel analyst Sam Wahab said: “Having the backing of the major shareholder looks to have put an end to this proposed offer.
“With IPGL not providing that backing, it is likely that other shareholders will follow their lead in our view.
“Reabold may now have to look at increasing its offer, or walking away from the deal entirely.”
Previously, on July 16, Deltic said the offer places no value on its significant non-cash assets and 'not least its share of two potential high impact exploration wells with partner Shell'.
The offer does not even reflect its existing cash balance (£13.2mln), added Deltic, which said it also had concerns over Reabold's existing investments.
The takeover would see Reabold shareholders own approximately 76.2% of the combined group's issued share capital and Deltic shareholders approximately 23.8%.
In Tuesday’s deals in London, Deltic shares were priced at 0.83p, down 2.59%.