Major Bowleven shareholder Waseem Shakoor described the deal as a knock down price after years of investment by the company.
Mr Shakoor said he was "shocked by the value destruction that has been crystallised by the deal" and warned he might vote against the deal and move to get chief executive Kevin Hart voted off the board.
Mr Shakoor said he would rather Bowleven sold than see the company remain under the leadership of what he called a failed management team.
Bowleven announced it has agreed a farm-out deal under which it will cede operational control of the Etinde permit.
This contains undeveloped oil and gas finds the company hopes to bring onstream.
The farm out deal appears to put a $500m value on the acreage although Bowleven may have spent more than that on it over the years.
New Age, an African firm with which Bowleven has been in dispute, and Russian oil giant LUKOIL will acquire significant stakes in Etinde.
Mr Hart hailed the deal as an endorsement of the value of the Etinde permit on which the company has been working for around 10 years.
"I am delighted that LUKOIL are joining us as a value-adding partner in Cameroon, alongside our existing co-venturer, NewAge.
LUKOIL are a major international integrated oil and gas group with extensive operating and marketing expertise globally and a track record of delivering world class oil and gas developments."
Mr Hart said Bowleven would be well positioned to fund its share of ongoing work on Etinde and to progress exploration work in Cameroon, Kenya and Zambia following the deal.
Shares in the firm closed up six per cent 2.25p at 42p following news of the deal.
Mr Shakoor said: "Many other shareholders like me, would rather vote for a sale of the entire company at the mooted farm-out value, approximately 70p per share. It would provide a cleaner exit for shareholders and would not leave a failed management team in charge of a large cash pile, where they could further destroy value."
Bowleven has raised around £370m from investors since 2005. It raised £13m at 45p per share in November.
Asked about Mr Shakoor's comments, Bowleven's finance director Kerry Crawford said it had done a deal that raised $250m for two thirds of its stake in Etinde and allows the firm to participate in the future upside potential through its remaining holding.
"We think it's a good deal for shareholders," she said.
Ms Crawford noted Bowleven was valued at $220m on the Aim market on Monday.
Pressed on Mr Shakoor's claim the management team had failed, she added: "We have taken Etinde significantly forward both discovering resource and been very successful with the drill bit and opening markets."
She said with a significant company like LUKOIL backing the Etinde project Bowleven could create further value for shareholders from its remaining 25% stake in the licence.
The farm-out deal with New Age has been agreed after it emerged that Bowleven had become embroiled in a legal dispute with the African firm's Camop subsidiary.
In January, the judge in a High Court action noted Camop had raised doubts about Bowleven's ability to deliver the Etinde scheme and the best development option.
Ms Crawford said an arbitration process involving the firms had been stayed. It will be dropped by both parties if the farm out completes.
New Age will increase its holding to 37.5% from 25%.
LUKOIL will acquire 37.5%.
Camop will assume operatorship of Etinde from Bowleven, which has faced funding challenges following delays with its plan to start production from Etinde.
In April the company said it had become more likely that it would make a decision about whether to sanction the huge investment required to develop finds on the permit around the end of this year, rather than by the summer.
In November, Bowleven had put the expected date of the decision back to mid-2014, rather than the end of last year.
In its interim results announcement in April Bowleven said:
"The Board believe that additional funds can be raised from any one of a number of sources ... but note that as this has not been secured at the date of this report it creates a material uncertainty which may cast significant doubt about the Group's ability to continue as a going concern."
The farm outs are conditional on them being approved by the Cameroon government and by Bowleven shareholders at a General Meeting.
Bowleven said recently it had invested $720m in Cameroon, around $540m net of contributions by partners. Ms Crawford said the bulk of investment went to Etinde.
Bowleven raised £55m at 650p per share in October 2005 under past management.
Mr Hart joined Bowleven in 2006 from Cairn Energy, which made big finds in India.
Shares in Bowleven traded at 386p in January 2011.
There are around 324m shares in the company in issue.