Robert Brian, a 10-year veteran of BP in Alaska, has filed a complaint against the UK company with the US Department of Labor, alleging "unlawful retaliation" for public criticisms of BP safety practices.

The complaint, to the department's Occupational Safety & Health Administration (OSHA), follows the outspoken union member's latest criticisms, arising from the explosion of a well in Alaska that seriously injured a worker.

Mr Brian, an instrument technician and operator, filed a complaint with OSHA after the August 16 explosion, which he believes could have been prevented.

After that, he said, his field supervisor, Randy Selman, ousted him from a meeting on safety, preventing his views from being heard. A week later, he said, George Blankenship, BP general field manager, approached him in "one of many intimidating, very unusual and unexpected meetings by a higher-ranking management official".

Mr Brian had sent Mr Blankenship an e-mail, telling him he no longer felt free to express his safety concerns. He said Mr Blankenship sought him out at the airport and "ominously instructed me to call him before I returned to work".

Mr Brian has not returned since. Such harassment, he claims in his complaint to OSHA, has been going on for years.

"We did receive a whistle-blower complaint about BP, and we will investigate it," said Richard Terrill, OSHA regional administrator in Seattle.

Ronnie Chappell, BP spokesman, said: "As a matter of policy we don't discuss litigation or personnel matters involving individual employees. We respect the right of employees to raise concerns in any forum they choose."

When Mr Brian complained during previous years, as a health and safety union representative, about what he believed were unsafe welding practices, he claimed BP concealed welding so he could not monitor procedures.

Mr Brian also claimed that last year Chris Phillips, BP vice-president, took the unusual step of seeking Mr Brian out in a remote work location, for a "passionate, though civil, exchange about safety issues".

He added that Steve Marshall, president of BP Alaska, called him at home following reports by an Alaska newspaper about BP health, safety and environmental issues.

"We take employee concerns seriously," BP's Mr Chappell said. "For that reason it is not unusual for members of the company's management team to contact workers who have raised concerns in order to learn about their concerns and to facilitate an appropriate response."

Mr Brian said: "I have taken enormous risks to my career by standing up for what is right, and I have been paying the price ever since."

Alaskan officials are to consider regulating some of BP's wells in the region after an explosion that seriously injured a worker and caused a spill.

Such regulation, to be considered at a hearing on November 14, would signal that the Alaska Oil and Gas Conservation Commission (AOGCC) no longer trusted the UK-based oil and gas company to regulate itself.

BP manages the operations of 1,600 Prudhoe Bay wells, owned by BP , ExxonMobil and Phillips Petroleum. Since an explosion of one well because of pressure problems on August 16, 260 have been highlighted as potentially problematic, requiring further safety tests. "The goal is to make the operations safer," said Dan Seamount, an AOGCC commissioner.

Charles Hamel, an advocate for BP workers in Alaska , said staff had complained about the fairness of BP's internal investigation. "One of the people in the investigation team was the one giving the 'verbal waiver' to flow the well without the proper diagnostics. He was, in effect, investigating himself," Mr Hamel said.

In response, Ronnie Chappell, BP spokesman, said the investigating team also included experts from outside the company and hourly workers.

Six weeks after the explosion BP is still declining to make public a copy of its investigation.

Some workers say they were told to keep copies secret, but BP insists the investigation has yet to be completed.

The explosion has created unease between some workers and management. Robert Brian, an instrument technician and operator, said BP had been using untrained personnel to return to service some of the problem wells shut down ater the explosion.

"I had untrained personnel come up to me and tell me that they were uncomfortable with bleeding off these wells as they were put on production," Mr Brian said.

"When I tried to bring our concerns up to my supervisor in a safety meeting with the other operators, I was asked to leave."

BP , which admits staffing difficulties, maintains that only qualified personnel work on the wells.

Mr Chappell said: "We have been unable to find a single instance in which an untrained person was involved in the start-up of one of these wells."

The AOGCC has scheduled the November public hearing to consider governing "the operation of development wells in all pools within the Prudhoe Bay Field with pressure communication or leaking in any casing, tubing or packer".