Nordic bank Nordea has sold all its shares in BP, accusing the oil giant of a lack of transparency over the US oil spill.
The bank said it had divested about 10m euros ($11.9m; £8.2m) spread across about 20 funds.
And it said it would halt investment in BP until further notice.
BP shares were one of the few risers on the FTSE 100 on Monday, although they have lost about a third of their value since the crisis started.
"The environmental catastrophe in the Mexican Gulf is an extraordinary situation given the size of the spill, weak response from BP, criminal investigation towards the company as well as anticipated risk for other accidents," Nordea said.
BP said it had been "open and transparent in every aspect of the response".
Given BP has a market capitalisation of about £81bn, Nordea is, a relatively small investor.
The Deepwater Horizon rig sank on 20 April after an explosion, killing 11 workers.
Both BP and the US government have been criticised for the response so far.
The spill has been described as the biggest environmental disaster in US history.
The oil has steadily spread east, and there are fears it could devastate the shoreline with the hurricane season coming up.
A containment cap on a ruptured well in the Gulf of Mexico is now funnelling off 10,000 barrels of oil a day, BP's chief executive Tony Hayward says.
The amount has risen since Saturday, and implies more than half the estimated 12,000 to 19,000 barrels leaking each day is now being captured.
In its latest update, BP said its cost of the spill response was now $1.25bn.
BP has been coming under fire for spending a reported $50m on TV advertising to improve its image while the crisis was still going on.
BP says it has spent more than $1bn so far on clean-up and containment efforts since the Deepwater Horizon rig accident.