NEW ORLEANS (AP) — Many fishing boats signed up to skim oil sit idle in marinas. Some captains and deckhands say they have been just waiting around for instructions while drawing checks from BP of more than $1,000 a day per vessel. Thousands of offers to clean beaches and wetlands have gone unanswered.

BP and the Obama administration faced mounting complaints Thursday that they are ignoring foreign offers of badly needed equipment and making poor use of the fishing boats and volunteers available to help clean up what may now be the biggest spill ever in the Gulf of Mexico.

Based on some government estimates, more than 140 million gallons of crude have now spewed from the bottom of the sea since the April 20 explosion that killed 11 workers on the Deepwater Horizon oil platform, eclipsing the 1979-80 disaster off Mexico that had long stood as the worst in the Gulf.

In recent days and weeks, for reasons BP has never explained, many fishing boats hired for the cleanup have done a lot of waiting around. At the same time, there is mounting frustration over the time it has taken the government to approve offers of help from foreign countries and international organizations.

The Coast Guard said there have been 107 offers of help from 44 nations, ranging from technical advice to skimmer boats and booms. But many of those offers are weeks old, and only a small number have been accepted, with the vast majority still under review, according to a list kept by the State Department.

A report prepared by investigators with the House Committee on Oversight and Government Reform for Rep. Darrell Issa, R-Calif., detailed one case in which the Dutch government offered April 30 to provide four oil skimmers that collectively could process more than 6 million gallons of oily water a day. It took seven weeks for the U.S. to approve the offer.

White House spokesman Robert Gibbs on Thursday scorned the idea that ‘‘somehow it took the command 70 days to accept international help.’’

‘‘That is a myth,’’ he declared, ‘‘that has been debunked literally hundreds of times.’’

He said 24 foreign vessels were operating in the Gulf before this week. He did not specifically address the Dutch vessels.

More than 2,000 boats have signed up for oil-spill duty under BP’s Vessel of Opportunity program. The company pays boat captains and their crews a flat fee based on the size of the vessel, ranging from $1,200 to $3,000 a day, plus a $200 fee for each crew member who works an eight-hour day.

Rocky Ditcharo, a shrimp dock owner in Buras, La., said many fishermen hired by BP have told him that they often park their boats on the shore while they wait for word on where to go.

‘‘They just wait because there’s no direction,’’ Ditcharo said. He said he believes BP has hired many boat captains ‘‘to show numbers.’’

‘‘But they’re really not doing anything,’’ he added. He also said he suspects the company is hiring out-of-work fishermen to placate them with paychecks.

Chris Mehlig, a fisherman from Louisiana’s St. Bernard Parish, said he is getting eight days of work a month, laying down containment boom, running supplies to other boats or simply being on call dockside in case he is needed. ‘‘I wish I had more days than that, but that’s the way things are,’’ he said.

Billy Nungesser, president of Louisiana’s hard-hit Plaquemines Parish, said BP and the Coast Guard provided a map of the exact locations of 140 skimmers that were supposedly cleaning up the oil. But he said that after he repeatedly asked to be flown over the area so he could see them at work, officials told him only 31 skimmers on the job.

‘‘I’m trying to work with these guys,’’ he said. ‘‘But everything they’re giving me is a wish list, not what’s actually out there.’’

A BP spokesman declined to comment.

Newly retired Coast Guard Adm. Thad Allen, the government’s point man for the response effort, bristled at some of the accusations in Issa’s report.

‘‘I think we’ve been pretty transparent throughout this,’’ Allen said at the White House. He disputed any suggestion that there aren’t enough skimmers being put on the water, saying the spill area is so big that there are bound to be areas with no vessels.

The Coast Guard said there are roughly 550 skimmers working in the Gulf, with 250 or so in Louisiana waters, 136 in Florida, 87 in Alabama and 76 in Mississippi, although stormy weather in recent days has kept the many of the vessels from working.

The frustration extends to the volunteers who have offered to clean beaches and wetlands. More than 20,000 volunteers have signed up to help in Florida, Alabama and Mississippi, yet fewer than one in six has received an assignment or the training required to take part in some chores, according to BP.

The executive director of the Alabama Coastal Foundation, Bethany Kraft, said many people who volunteered are frustrated and angry that no one has called on them for help.

‘‘You see this unfolding before your eyes and you have this sense that you can’t do anything,’’ she said. ‘‘To watch this happen in our backyard and not be able to help is hard.’’

About 225 foundation volunteers have helped watch for oil and document coastal conditions, she said, but BP’s rules require training for anyone touching oily material. And the company is using paid workers for nearly all such projects.

While the leak continued spewing crude into the Gulf, the remnants of Hurricane Alex more than 500 miles to the west were still being felt Thursday in the form of rough seas that slowed the cleanup, though some skimming had resumed.

Some government estimates put the amount of oil spilled at 160 million gallons. That calculation was arrived at by using the rate of 2.5 million gallons a day all the way back to the oil rig explosion. The AP, relying on scientists who advised the government on flow rate, bases its estimates on a lower rate of 2.1 million gallons a day up until June 3, when a cut to the well pipe increased flow.

By either estimate, the disaster would eclipse the Ixtoc disaster in the Gulf two decades ago and rank as the biggest offshore oil spill during peacetime. The bill spill in history happened in 1991 during the Persian Gulf War, when Iraqi forces opened valves at a terminal and dumped about 336 million gallons of oil.

The total in the Gulf disaster is significant because BP is likely to be fined per gallon spilled. Also, scientists say an accurate figure is needed to calculate how much oil may be hidden below the surface, doing damage to the deep-sea environment.

‘‘It’s a mind-boggling number any way you cut it,’’ said Ed Overton, a Louisiana State University environmental studies professor. ‘‘It’ll be well beyond Ixtoc by the time it’s finished.’’

And passing Ixtoc just before the July Fourth weekend, a time of normally booming tourism, is bitter timing, he said.

In other developments:

The House passed the first major bill related to explosion, voting to allow families of those killed and injured workers to be compensated far more generously than current law allows. The measure now goes to the Senate.

An animal welfare group said in a lawsuit that BP’s practice of incinerating the oil is probably burning endangered sea turtles alive. BP spokesman Mark Proegler replied: ‘‘I can’t say for sure we’ve never burned any, but every effort is taken to avoid that.’’

The Coast Guard and the Environmental Protection Agency are tightening up their oversight of BP and its contractors cleaning up the oily sand.