Lord Robertson of Port Ellen, deputy chairman of TNK-BP, today added his voice to growing anger over the departure of chief executive, Robert Dudley, from Moscow following "a campaign of harassment" by Alfa Access and Renova (AAR), BP’s Russian joint-venture partners.

It emerged yesterday that Mr Dudley had left Russia after a refusal by Russia’s Federal Migration Service to grant him a visa and investigations by state security agents.

His departure is the latest twist in a dramatic row with AAR, BP’s Russian joint venture partners.

Lord Robertson said today: "Alfa Access and Renova are threatening the viability of this historic joint venture that has been so good for Russia, and for all its shareholders, since it was formed with such high hopes in 2003.

“There is a legitimate way of bringing about change in a company — through negotiation and discussion. AAR’s efforts to wrest control of the company through illegitimate means are damaging the company and, regrettably, Russia’s reputation among international investors."

Yesterday, Tony Hayward, chief executive at BP told The Times: "We intend to hold our ground,” adding: "We are not going to be intimidated by their strong-arm tactics.”

However, he insisted the attacks were not being directed by the central government.

Instead, Mr Hayward said AAR, the consortium of four Russian oligarchs which is BP’s 50:50 joint venture partner in TNK-BP, had been “manipulating low-level” elements of the Russian state using underhand practices.

Mr Hayward also was at pains to dismiss AAR’s claims that the row was about TNK-BP's poor performance.

He said the company, Russia’s third largest producer of crude oil, had been “stellar” since its formation in 2003.

“TNK-BP has the highest reserve replacement ratio and lowest development costs of any oil company in Russia,” he said.

“This is not about performance. It’s a dispute between shareholders.”

AAR has insisted that its efforts to oust Mr Dudley have been driven by his failure to act in the interests of all shareholders and because of weak financial performance.

However, Mr Hayward gave little indication as to how BP intended to resolve the dispute, declining to comment on ongoing discussions regarding ownership. He insisted that BP intended to stay in Russia for the long term.

“This has been a very succesful investment for BP,” he said, adding that the group would use “every means at our disposal that remains well within the law” to protect its investment.

It would include legal action to recover losses associated with any breach of the original shareholder agreement.

Mr Hayward also said that BP would seek to isolate AAR using other measures.

The four oligarchs — Len Blavatnik, Mikhail Fridman, German Khan and Viktor Vekselberg — have strong connections with a range of Western companies and institutions.

Mr Blavatnik’s Access Industries group owns 4 per cent of Warner Music, of which he was a board director until January this year.

Goldman Sachs offered Mr Blavatnik a multibillion dollar credit line to help him fund the acquisition of chemicals group Lynondell.

A string of foreign executives working for TNK-BP remain in Russia, including Timothy Summers, chief operating officer, James Owen, chief financial officer, and Tony Considine, executive vice president of TNK-BP’s downstream business.

Times Recommends

• UK savers left in lurch as Icesave crumbles
• RBS shares close under £1 on bailout fears
• Asian stocks rebound on Australian rate cut