WASHINGTON (Reuters) — British energy giant BP Plc's stock price plunged to a 14-year low in US trading as the Obama administration threatened to impose new penalties on it over the worst oil spill in US history.

And Gulf Coast fishermen, businesses and property owners who have filed damage claims with BP over the oil spill are angrily complaining of delays, excessive paperwork and skimpy payments that have put them on the verge of going under as the financial and environmental toll of the disaster grows by the day.

Turning up the heat on the beleaguered company, a senior US Justice Department official said after the markets closed that the department was "planning to take action" to ensure BP had enough money on hand to cover damages from the Gulf of Mexico spill.

Earlier, BP depositary shares trading in New York fell nearly 16 percent to close at $29.20, their lowest level since August 1996, on growing worries about the costs the company will have to assume.

US Interior Secretary Ken Salazar told a Senate hearing he would ask the British oil giant to repay the salaries of any workers laid off because of the six-month moratorium on deepwater exploratory drilling imposed by the US government after the spill.

BP's total bill so far, including cleanup costs, has reached $1.25 billion and the US government has already said it will have to pay billions more in penalties.

The White House echoed Salazar's comments.

"The moratorium is as a result of the accident that BP caused. It is an economic loss for those workers, and ... those are claims that BP should pay," White House spokesman Robert Gibbs told a briefing.

BP believes it may be heading for a showdown with the White House over widening demands on spill-related costs, a BP source said.

While the company has said it will pay for the clean-up and direct damages to those affected by the spill, the moratorium was a government decision and costs related to it were a different matter, the source said.

Earlier, the company's stock closed down four percent in London on concerns the company might have to suspend its dividend payment.

Shrimpers, oystermen, seafood businesses, out-of-work drilling crews and the tourism industry all are lining up to get paid back the billions of dollars washed away by the disaster, and tempers have flared as locals direct outrage at BP over what they see as a tangle of red tape.

"Every day we call the adjuster eight or ten times. There's no answer, no answering machine," said Regina Shipp, who has filed $33,000 in claims for lost business at her restaurant in Alabama. "If BP doesn't pay us within two months, we'll be out of business. We've got two kids."

An Alabama property owner who has lost vast sums of rental income angrily confronted a BP executive at a town meeting.

The owner of a Mississippi seafood restaurant said she is desperately waiting for a check to come through because fewer customers come by for shrimp po-boys and oyster sandwiches.

Some locals see dark parallels to what happened after Hurricane Katrina, when they had to wait years to get reimbursed for losses.

"It really feels like we are getting a double whammy here. When does it end?" said Mark Glago, a New Orleans lawyer who is representing a fishing boat captain in a claim against BP.

BP spokesman Mark Proegler disputed any notion that the claims process is slow or that the company is dragging its feet.

Proegler said BP has cut the time to process claims and issue a check from 45 days to as little as 48 hours, provided the necessary documentation has been supplied.

BP officials acknowledged that while no claims have been denied, thousands and thousands of claims had not been paid by late last week because the company required more documentation.

US Coast Guard Admiral Thad Allen – head of the administration's response to the disaster – also confronted BP over the complaints about the claims process, warning the company in a letter: "We need complete, ongoing transparency into BP's claims process including detailed information on how claims are being evaluated, how payment amounts are being calculated and how quickly claims are being processed."

Admiral Allen added: "The federal government and the public expects BP's claims process to fully address the needs of impacted individuals and businesses," Allen said in a June 8 letter to BP.

The admiral this week created a team including officials from the Federal Emergency Management Agency to help with the damage claims. It will send workers into Gulf communities to provide information about the process. He also planned to discuss the complaints with BP officials Wednesday.

Under federal law, BP is required to pay for a range of damage, including property losses and lost earnings.

Residents and businesses can call a telephone line to report losses, file a claim online and seek help at one of 25 claims offices around the Gulf. Deckhands and other fishermen generally need to show a photo ID and documentation such as a pay stub showing how much money they typically earn.

To jump-start the process, BP was initially offering an immediate $2,500 to deckhands and $5,000 to fishing boat owners. Workers can receive additional compensation once their paperwork and larger claims are approved. BP said it has paid 18,000 claims so far and has hired 600 adjusters and operators to handle the cases.

At a congressional hearing, one lawmaker asked US Associate Attorney General Thomas Perrelli whether the Justice Department had the ability to issue an injunction against BP to stop it paying its dividend.

"We are looking very closely at this and we are planning to take action," he said.

BP officials have said they have enough cash to handle the crisis. But the market has shown less confidence. With Wednesday's share price drop in New York, BP has given up more than half its market value since the crisis began.

"The confidence in BP being able to stop the oil leak and deal with the ecological aftermath has disappeared," said TD Ameritrade chief derivatives strategist Joe Kinahan.

Illustrating analysts' anxiety about BP's dividend, in the past two days alone, seven have cut their expectations on the likely payout. http://link.reuters.com/jeb29k.

The cost of protecting BP's debt against default hit new highs on Wednesday.

The spill began on April 20 after an oil rig exploded, killing 11 workers and rupturing the deep-sea well. It has caused environmental devastation along the US Gulf Coast and threatens lucrative fishing and tourist industries.

The Obama administration, facing growing voter discontent over its own handling of the crisis, has sought to distance itself from the company.

US President Barack Obama has also toughened his rhetoric in recent days and said in an interview this week he would fire BP CEO Tony Hayward if he worked for him.

BP has paid out close to $50 million in damages claims so far along the Gulf Coast — mostly to fishermen, shrimpers, oystermen and boat operators who say their livelihoods have been impacted by the spill.

Meanwhile, BP America President Lamar McKay, along with top executives from Exxon Mobil Corp, Chevron Corp, ConocoPhillips and Shell Oil Co, were called to testify at a June 15 congressional hearing that will look at the oil spill and America's energy future.

At the scene of the spill, BP continued to siphon off oil from its blown-out oil well in the Gulf of Mexico.

Allen told reporters that BP planned to move another rig to the spill site on June 14. This would enable the company to boost its capacity to collect oil from the well to 28,000 barrels (1.18 million gallons/4.45 million litres) a day, he said.

Allen did not indicate this meant the flow rate of the oil could be as high as 28,000 barrels a day, but his comments are likely to underscore that neither BP nor the government have yet managed to determine just how much oil is gushing out.

Government scientists have estimated that the leak spews 12,000-19,000 barrels a day, with one estimate as high as 25,000 barrels.

They are due to present revised estimates later this week or early next week.

The spill has already fouled wildlife refuges in Louisiana and barrier islands in Mississippi and Alabama.

It has also sent tar balls ashore on beaches in Florida. One-third of the Gulf's federal waters remains closed to fishing and the toll of dead and injured birds and marine animals is climbing.

BP's latest containment effort, which follows a series of earlier failed attempts, involved placing a containment cap with a seal on a deep-sea pipe from which the oil is gushing.

But the ultimate solution to the leak lies in the drilling of a relief well and that won't be completed before August.