Oil company BP has come under fire from both shareholders and protesters at its annual meeting as the anniversary of the Gulf of Mexico oil disaster looms.

Activists wearing T-shirts emblazoned with the slogan "No Tar Sands", in protest against BP's oil extraction operations in Canada, were dragged out of the ExCeL Centre in London as they tried to stage a demonstration. A group of fishermen and women from the Gulf coast who say their livelihoods have been destroyed by the oil spill that followed the explosion of BP's Deepwater Horizon rig last April were denied entry to the meeting despite holding proxy documents for the event which should have allowed them in.

A quarter of investors voted against the re-election of BP's safety committee in a damning indictment of the recent record of accidents.

The meeting also saw the board grilled over its delayed £10bn share-swap and exploration deal with Russian state-controlled oil company Rosneft. BP said it had been given a one-month extension to hold further talks over the troubled joint venture.

The protesters had flown in from the US to draw attention to what they say is evidence that the Gulf continues to be badly affected by last year's spill. Louisiana fisherwoman Diane Wilson was arrested for breach of the peace after she smeared herself in an oil-like substance as she tried to gain access to the conference centre.

During a tense meeting, BP chairman Carl-Henric Svanberg tried to prevent Antonia Juhasz, an activist promoting a book about the Gulf spill, from reading a statement from Keith Jones, whose son Gordon was one of the 11 workers to die when the Deepwater Horizon exploded.

"His son died aboard the rig and you don't want to hear his voice?" she interrupted, before she read out the statement: "This was not an act of God. BP and Halliburton could have prevented the blow-out. You were rolling the dice with my son's life and you lost."

She also claimed the large parts of the sea bed were dead zones because of the oil and dispersant that she said had sunk to the bottom.

In response to her comments, BP chief executive Bob Dudley read out the names of the 11 men who died when the rig exploded. He said nothing could be done to bring the 11 men back, that the accident had "shocked and saddened us all", and the company would do everything it could to make sure it did not happen again.

Dudley continued: "I disagree with your assessment that the BP oil spill has ruined life on the bottom of the ocean. It's a lifeless zone in some of these areas because of the fertiliser coming down ...You say it's because of the oil, which you can't see and I can't see."

Mike Roberts, one of the three Louisiana shrimpers barred entry, told the Guardian outside: "That is typical tactics from BP -- they say something that sounds good. When you have got that kind of money you write your kind of history and make your own reality."

Roberts, from Grande Isle on the coast, has not been fishing since the spill and says few people in the Gulf feel confident about eating fish caught there. He added: "We came all the way from Louisiana. We weren't going to be rowdy. We were here, dignified and respectful, on their terms.They looked at our passports and asked us if we were all from Louisiana. They didn't let us in because they didn't want the truth to be told."

Some 25% of shareholders voted against the re-election of Sir William Castell, BP's senior non-executive director and head of the safety, ethics and environment assurance committee. The remuneration report was also unpopular, with an 11.1% vote against due to the bonuses paid to the finance director and the head of refining last year, as well as the £1m golden goodbye for former chief executive Tony Hayward. Another 7.1% voted against the re-election of Svanberg as chairman, who rebutted criticism that he took a hands-off approach to the crisis last year.

BP said it hoped the extra month would enable it to salvage its controversial alliance with Rosneft which is being blocked by AAR, which represents the interests of three Russian oligarchs who are partners with BP in their TNK-BP venture.

Dudley said BP had made a "fair offer" to buy out half of TNK-BP, as well as offering it involvement in the Rosneft deal, but added: "We are not going to offer a large amount or significant shareholdings."

Stan Polovets, chief executive of AAR, responded: "BP has never made a constructive proposal to turn the Rosneft deal over to TNK-BP as our shareholder agreement requires. AAR is not interested in the selective parts of the deal that BP feels it can give up."