Harding also responded to criticism over the board's decision not to allow shareholders a vote on the merger, saying the deal was in the best interest of shareholders.

Addressing shareholders at the company's annual general meeting yesterday, Harding said ROC had consulted with the Australian Securities Exchange on the merger and was advised a shareholder vote was not required.

"This is in accordance with the ASX listing rules which have allowed this type of transaction for the last 15 years," he said.

"The board decided to proceed with the merger without a shareholder vote because the transaction is in total alignment with our stated growth strategy.

"It is with Horizon Oil, which we know well, with assets we believe will add significantly to the ROC business in the long term and we have conducted very extensive due diligence and the board unanimously believe that this transaction will create shareholder value.

"This transaction delivers a far greater growth path than we could ever achieve on our own.

"We believe the merger is in the best interests of shareholders."

Investment house Allan Gray called for an extraordinary general meeting to try and allow ROC Oil shareholders to vote on the merger it previously called a "stupid deal".

But Harding urged shareholders to vote against the proposed changes to ROC's constitution, which would allow shareholders to vote on the deal.

"As you are probably aware, interests associated with Allan Gray have requisitioned a general meeting to consider an amendment to ROC's constitution," Harding continued.

"Shareholders will receive a notice of meeting and explanatory statement next week, which will include all material information for shareholders to consider in connection with this requisition.

"Shareholders should carefully consider these materials.

"Your directors will recommend that you vote against the change."

Harding said the transaction with Horizon was one of the best value accretive and complementary deals he had seen.

"An opportunity like this presents itself very rarely and is transformational to ROC and Horizon," he added.

"We know the Horizon team and assets well and this gives us great confidence in our decision to proceed."

The merger has been structured to ensure ROC will continue as an ASX-listed company and will maintain the ROC name.