The group of billionaire oligarchs who are BP’s partners in TNK-BP have threatened to thwart any attempt by the UK oil group to sell its stake in the joint venture, creating fresh risks for chief executive Bob Dudley as he moves to execute one of the biggest divestments in BP’s history.

The partners, known as AAR, say their shareholder agreement prevents BP giving out confidential information about TNK-BP to any third party without AAR’s consent – including details of the agreement itself.

“The same goes for sharing any operational data – such as capital expenditure plans, projections for production growth and reserve replacement, sales contracts – all of which are covered by confidentiality clauses in the agreements between BP and AAR,” said Mikhail Loskutov, an AAR spokesman.