WASHINGTON - BP's estimate that only 5,000

barrels of oil are leaking daily from a well in the Gulf of Mexico,

which the Obama administration hasn't disputed, could save the company

millions of dollars in damages when the financial impact of the spill is

resolved in court, legal experts say.

A month after a surge of gas from the undersea

well engulfed the Deepwater Horizon offshore drilling rig in flames and

triggered the massive leak that now threatens sea life, fisheries and

tourist centers in five Gulf coast states, neither BP nor the federal

government has tried to measure at the source the amount of crude

pouring into the water.

BP and the Obama administration have said

they don't want to take the measurements for fear of interfering with

efforts to stop the leaks.

That decision, however, runs counter to BP's own regional plan

for dealing with offshore leaks. "In the event of a significant release

of oil," the 583-page plan says on Page 2, "an accurate estimation of

the spill's total volume . . . is essential in providing preliminary

data to plan and initiate cleanup operations."

Legal experts said

that not having a credible official estimate of the leak's size

provides another benefit for BP: The amount of oil spilled is certain to

be key evidence in the court battles that are likely to result from the

disaster. The size of the Exxon Valdez spill in Alaska, for example,

was a significant factor that the jury considered when it assessed

damages against Exxon.

"If they put off measuring, then it's

going to be a battle of dueling experts after the fact trying to

extrapolate how much spilled after it has all sunk or has been carried

away," said Lloyd Benton Miller, one of the lead plaintiffs' lawyers in

the Exxon Valdez spill litigation. "The ability to measure how much oil

was released will be impossible."

"It's always a bottom-line

issue," said Marilyn Heiman, a former Clinton administration Interior

Department official who now heads the Arctic Program for the Pew

Environment Group. "Any company wouldn't have an interest in having this

kind of measurement if they can help it."

The size of the spill

has become a high stakes political controversy that's put the Obama

administration and the oil company on the defensive. In congressional

testimony Wednesday, an engineering professor from Purdue University in

West Lafayette, Ind., said that based on videos released Tuesday he

estimated that the well was spewing at 95,000 barrels, or 4 million

gallons, of oil a day into the gulf.

The Obama administration

Thursday demanded that BP publicly release all information related to

the disaster.

BP officials had pledged in congressional

testimony to keep the public and government officials informed, Homeland

Security Secretary Janet Napolitano and Environmental Protection Agency

Administrator Lisa Jackson said in a letter to BP chief executive

officer Tony Hayward.

"Those efforts, to date, have fallen short

in both their scope and effectiveness," they wrote.

That letter

came after members of Congress made similar demands of BP, leading to

the release Tuesday of the new videos. One showed oil still billowing

from one underwater pipe, despite an insertion tube BP now says is

capturing 5,000 barrels of crude a day _ its entire initial estimate of

the spill. The other showed a previously unseen leak spewing clouds of

crude from just above the well's dysfunctional blowout preventer.

The EPA on Thursday ordered BP to switch to a less toxic version of the

chemical mix it's using to disperse the oil. The EPA also for the first

time posted on its website BP's test data of the dispersant's use in

deep water. Those orders came days after McClatchy reported doubts about

the dispersant's safety and members of Congress made a similar demand.

Scientists and environmentalists praised the government for demanding

that more information be made public.

"This is exactly the role

the government needs to be playing - they need to be overseeing BP's

actions to assure that health and natural resources are protected, as

much as possible, and that information is available to the public," said

Gina Solomon, a senior scientist with the Natural Resources Defense

Council.

This video, released

Tuesday, shows billowing clouds of oil despite the presence of the

insertion tube, visible to the right of the broken pipe

John Curry, a BP spokesman, said he hadn't seen the letter from

Napolitano and Jackson and couldn't comment specifically, but added:

"We're just trying to provide the information people are asking for at

the same time we are trying to position a lot more resources to stop the

flow of oil."

Curry offered no new estimate of how much oil is

flowing from the leaks, but acknowledged that capturing 5,000 barrels of

oil a day in the insertion tube is evidence that the official

5,000-barrel per day estimate is low.

"We've said at best it's a

highly imprecise estimate," Curry said.

Curry said he knew of no

efforts by BP to use its robotic equipment on the sea floor to measure

the flow, but said that the efforts were entirely focused on containing

the spill.

BP agreed Thursday to allow the posting of a live feed

of the video of the oil spill, which lawmakers said would help

scientists arrive at independent estimates of the spill.

"I'm

sitting here looking at it right now, and it ain't 5,000 barrels a day,

I'll guarantee it," said Bob Cavnar, a Houston engineer and blogger

who's been involved in oil and gas exploration and production.

"In Houston, there's about 125,000, 150,000 engineers," he said. "And

all the engineers can calculate what the flow is."

The feed

eventually was overwhelmed by the number of people trying to view it and

was removed from congressional websites.

This video, released

Tuesday, provided the first public view of a second leak near the well's

dysfunctional blowout preventer.

Calling the disaster

site a "crime scene," Larry Schweiger, the president of the National

Wildlife Federation, accused BP of a cover-up.

"BP cannot be

left in charge of assessing the damage or controlling the data from

their spill," Schweiger said. "The public deserves sound science, not

sound bites from BP's CEO."

White House press secretary Robert

Gibbs denied that the government was trying to cover up the size of the

spill.

"The best and brightest minds in all of this government,

and in the scientific community and in the world of commerce are focused

on this problem. Everything that can be done is being done," he said.

Sens. Bill Nelson of Florida and Barbara Boxer of California, both

Democrats, called on the Justice Department to investigate BP's drilling

permits to determine whether the company had misled the government by

claiming it had the technology needed to handle a big spill.

Since the spill, BP has announced five different approaches to sealing

the leak. Three of those have been at least partially used: a 78-ton

containment dome that failed; a small "top hat" dome that was placed on

the seafloor May 11 but hasn't been used, and the insertion tube now

siphoning a fraction of the spill. Of the two others, the "junk shot,"

which would fire shredded tires and debris into the damaged blowout

preventer, is rarely mentioned, and the "top kill," which would force

mud into the blowout preventer, may be tried this weekend.

National Oceanic and Atmospheric Administration head Jane Lubchenco told

reporters on Thursday that a team of government scientists was

assembled this week, a month after the spill began, to try to come up

with a better estimate of the leak's volume.

She said the

5,000-barrel estimate was based on visual observations on the surface.

"As the spill increased in size and began to break up it was no longer

possible to use that effort, which is why we have shifted to using

multiple paths to try to get at better estimates," she said.

Scientists have the instruments and the knowledge needed to figure out

the flow rate, and several have complained publicly that they were

turned down when they offered to help, as McClatchy reported Tuesday.

"The decision was made that the first priority had to be to stop the

flow," Lubchenco said. Robotic vehicles were being used for that purpose

and there was limited space for more of them to operate there at the

same time, she said.

(Margaret Talev and David Lightman contributed to this

article.)