The boardroom battle at TNK-BP descended into outright mudslinging over the long holiday break, with the Russian shareholders threatening to have BP-nominated directors disbarred by a Moscow court this week and BP's chairman accusing them of using illegal "corporate raiding" tactics.

The chief executive of AAR, the consortium representing the Russian shareholders, insisted in an interview Saturday that the dispute centered only around mismanagement by BP officials.

"BP is trying to paint this as political pressure or pre-sale posturing, trying to deflect attention away from the core issue," the chief executive, Stan Polovets, said. "There should be no illusions about this: It is about mismanagement of the company, not politics or change of ownership."

A BP official countered that AAR was simply trying to seize control of the 50-50 joint venture.

The dispute, seen as a litmus test of foreign investors' rights, heated up Wednesday, when AAR said it would seek an injunction to have TNK-BP CEO Robert Dudley and four other BP-nominated directors of TNK-BP dismissed over an "illegal board meeting."

AAR also said it would seek to have a 2003 agreement on BP employees working inside TNK-BP as secondees annulled by the Stockholm Arbitration Court and would seek to have foreign specialists employed directly by TNK-BP instead.

"This is just a return to the corporate raiding activities that were prevalent in Russia in the 1990s," BP chairman Peter Sutherland told reporters in Stockholm on Thursday. "Prime Minister [Vladimir] Putin has referred to these tactics as relics of the 1990s, but unfortunately our partners continue to use them and the leaders of the country seem unable or unwilling to step in."

The broadside ­ the strongest yet by a BP official ­ prompted a protest from Alfa Group chairman Mikhail Fridman, who together with billionaires German Khan, Len Blavatnik and Viktor Vekselberg controls 50 percent of TNK-BP through AAR.

Sutherland's comments were "unhelpful and, frankly, insulting to the Russian leadership," Fridman said in a statement, also released Thursday.

The dispute could worsen Monday, when Fridman is expected to set out the Russian partners' grievances at a Moscow news conference.

AAR's threats of legal action and complaints about BP's role "are all red herrings," a source close to BP said Sunday. "AAR is trying to gain control of the company."

The court cases, however, could strip BP of much of its managerial control of TNK-BP and make it easier for a state company to take over.

Talks between the two sides in London broke down Wednesday after an AAR deadline expired. AAR was demanding Dudley's ouster and equal representation on the boards of TNK-BP, which controls the company's assets in Russia, and its Russian subsidiaries.

Yet, in a possible way out of the dispute, AAR and BP agreed that AAR shareholders could have an option to convert some or all of their shares into BP shares, representatives of both sides said. BP is understood to be in favor of such a swap and willing to sell it on to a state company such as Gazprom or Rosneft as long as it receives a fair price for the billionaires' stake.

Polovets said there were "seven specific violations of Russian law in the way that the [board] meeting was called and conducted. We are calling for decisions taken at the illegal board meeting to be annulled."

A TNK-BP source said the June 3 meeting was called without sufficient notice.

The BP source. who spoke on condition of anonymity citing the sensitivity of the situation, countered that the BP nominees on the TNK-BP board had not held an illegal board meeting but had properly called an annual shareholders meeting for June 26 so that dividends for 2007 could be paid.

During a 2 1/2-hour interview in a cafe next to TNK-BP's head office on Arbat, Polovets, a former Exxon and Ernst & Young executive, fielded several calls on his cell phone, including from Fridman and Khan, who is also TNK-BP's influential executive director, and signed a sheaf of documents brought to the cafe by an assistant.

Polovets explained that the Russian shareholders had expressed their concerns to BP about the way the company was being run for some time but had only decided to go public after Dudley aired their differences in an interview with Vedomosti last month.

TNK-BP was "not realizing its true potential" under BP-appointed managers, Polovets said.

"In 2003, TNK and LUKoil were worth about the same, $16 billion to $17 billion," Polovets said. "Now LUKoil is worth more than $95 billion, and we're worth $38 billion. The only major oil company that has done worse than ours [over the same period] is BP itself."

Polovets said an increase in TNK-BP's production before the 2003 merger had been followed by a flattening-off of growth.

Vladimir Buyanov, a spokesman for BP in Moscow, rejected the claim, citing a BP financial statement showing that total oil and gas production had risen by 30 percent since 2003.

The issue of secondees has been a major battleground between BP and AAR this year, as some 150 foreign specialists were found not to have valid work visas and permits and then denied entry to TNK-BP's offices.

Polovets said the Russian shareholders' position had been misrepresented as being against foreign managers per se, when in fact they just wanted to convert these positions from BP secondees ­ employees of BP "lent" to TNK-BP ­ into permanent TNK-BP jobs held by talented professionals from anywhere around the world.

"BP has tried to portray the Russian shareholders as anti-Western and anti-expat, but this is blatantly false. Before the merger, TNK had over 20 expats in senior positions, more than any other Russian oil company then," he said.

The original agreement with BP on secondees, to provide technical expertise to TNK-BP where it was needed, had been subverted, Polovets said.

"It was expected that the secondees would be based mostly in the regions, where our operating subsidiaries are located. But in reality, the agreement was transformed into an instrument to create a parallel management structure inside the headquarters, with no accountability to TNK-BP."

Some of the BP secondees come in with an attitude of "arrogance and superiority," Polovets said. "A number of senior Russian managers have complained to AAR that BP executives have often made them feel like aboriginals who are being taught by BP the most basic things [on] how to run an oil company.

"From BP's point of view, it's rational to have secondees. … They want to control these assets and run TNK-BP as a BP subsidiary with BP managers."

Other issues, such as BP rejecting an AAR proposal to hold an initial public offering in London last year and for downstream projects in the Baltics, Central and Eastern Europe also irked the Russian side, Polovets said.

In response to Fridman's comments Thursday, the BP spokesman said the company "plans to be in Russia for the long term. We are investing for the future and not just for quick cash returns. The government's application of the rule of law will help BP achieve that aim."

The source close to BP added Sunday that Fridman and his AAR partners were "looking for short-term gain in the next six to 12 months."

An observer familiar with the shareholders' dispute said Sunday that the newly aggressive attitude shown by Fridman and his AAR partners was not due to a desire to improve corporate governance at TNK-BP, but a desire to cash out.

He also rejected AAR's claim that BP's strategy had hurt TNK-BP and that BP's share price had suffered because of poor management.

"The reason why BP's share price has performed so poorly is specifically because of the uncertainty and risk in its Russian business," the person said on condition of anonymity, citing the political sensitivity of the issue.