Anti-BP protesters from Greenpeace today disrupted a speech by the company's chief of staff, Steve Westwell, at a major oil conference in London, urging the company to change its ways following the Deepwater Horizon disaster.

Westwell was delivering the speech in place of the oil giant's beleaguered chief executive, Tony Hayward, who last night cancelled what would have been his first public appearance in the UK since the oil spill in the Gulf of Mexico began.

Westwell's speech, to oil executives and energy ministers at the World National Oil Companies Congress, was interrupted when two female protesters from Greenpeace, Emma Gibson and Katie Swan, approached the stage holding a banner which read "Go Beyond Petroleum".

"We need to speed up progress and make a push to end the oil age," Gibson told the audience, before being bundled off by security. Before the protest, Hayward's stand-in had apologised for the BP chief executive's absence, saying: "He is genuinely sorry he couldn't be here, especially with so many friends in the conference. But his schedule is under incredible pressure at the moment."

Speaking after they had been ejected from the conference, Swan told the Guardian that she and Gibson had gone ahead with the protest despite Hayward's no-show as it was a chance to address the oil industry.

"We wanted to use the opportunity to speak to BP and push it to change things. BP shouldn't be drilling in deep water and it shouldn't extract oil from the Canadian tar sands."

Swan studied in Louisiana for four years, and was very concerned about the environmental and economic damage caused by the oil spill.

"It looks like irreparable damage has been done. People's lives will have been changed forever," Swan said.

Gibson said that BP was in "severe trouble" because it had not listened to activists in the past, and had instead pushed on with riskier projects.

"If they had heeded our advice over many years about the need to deliver genuine renewable energy sources, they would not be facing a $40bn (£24bn) disaster today," she said.

Hayward heading to Russia?

Westwell, who arrived through the back entrance at The Grange St Paul's hotel to avoid journalists, insisted that BP's commitment to clean up the oil spill would last longer than the press interest in the story.

"When the media has left the Gulf and the headlines have gone elsewhere we will still be there helping," he said.

Westwell said the company was now capturing up to 25,000 barrels a day in the Gulf of Mexico and described the financial consequences of the spill as severe, but reiterated BP would come through it.

So far, BP has spent $2bn fighting the spill and compensating victims since the Deepwater Horizon oil rig explosion on 20 April.

Hayward's non-appearance was the talk of the conference this morning. Paul Gilbertson, one of the organisers, described it as a "disappointment". Hayward has also pulled out of an appearance at the National Portrait Gallery in London tonight where he was due to open an awards ceremony.

Hayward is reportedly making a trip to see Russian president Dmitry Medvedev to reassure him that BP remains a robust company. Its joint venture with TNK is responsible for 25% of BP's revenues.

The BP boss was pilloried for attending a yacht race around the Isle of Wight on Sunday, while the company battles to contain the thousands of barrels of oil spewing into the Gulf of Mexico every day.

Last night celebrities in New York and Los Angeles came rushing to the rescue as the Larry King Live Show turned itself over to two hours of fundraising to help the affected people and animals of the Gulf region. The line-up included Sting, who performed his song Fragile, Robert Redford and Cameron Diaz.

The US TV show host explained the purpose of his CNN telethon in characteristically eloquent fashion. "Remember bureaucracy is slow; you can hear about billions being donated but it don't get there tomorrow. We're going to do our best to get it there pronto."