The GCA report would strengthen DNO's hand if it valued Faroe at or under its 152 pence per share offer, or it could pressure it to raise its offer. Faroe has urged its shareholders to reject the offer, which valued it at around $768 million.

Faroe, whose share price has slipped under 152 pence on several occasions in recent trading, also announced on Thursday it would plug and abandon its Cassidy well, the success of which could have given the shares a boost.

Faroe is due to publish the result of the Brasse East exploration well during the hostile bid period, which has an initial deadline of Jan. 2 but can be amended and extended until Feb. 10.

DNO, which has built up a 29.9 percent stake in Faroe, reiterated on Thursday its cash offer was "full and fair, even generous ... It is doubly so in an increasingly uncertain oil and equities market."

Faroe has until Jan. 20 to publish significant relevant information with regard to the offer, adding it planned to publish the independent valuation ahead of that date.

"GCA's ... report needs be a 'current' valuation of the assets and therefore must reflect the latest available information on Faroe's assets as at the report date which will therefore include the latest Brasse East drilling results subject to completion of drilling operations," Faroe said.

DNO earlier on Thursday called for Faroe to prove its claims.

"If Faroe genuinely believes the company is worth more than 152 pence per share, why does it not publish a robust valuation report and provide important updates on financial and operational matters, including the status of the Brasse East well, to support this claim?," DNO said in a statement.

($1 = 0.7907 pounds)

(Reporting by Shadia Nasralla and Gwladys Fouche; Editing by Mark Potter)