The chief executive of General Motors apologised for asking for US taxpayers' money today as the Big Three of the car industry prepared to plead with the Congress for more than £23 billion in loans.

General Motors (GM), Chrysler and Ford were appearing before congressional committees yesterday and today to ask for $34bn of federal assistance (£23.1 bn) after both GM and Chrysler said they would not survive beyond the end of the month without the rescue package.

The so-called Big Three submitted separate revised plans for their survival on Tuesday in a bid to convince the panels to call members of the US Congress back to Washington for a special session to vote on the car industry bail-out next week.

It is the second time the senior executives will face the hearings after they failed to convince a sceptical Congress they were worthy of the loans last month.

Today, GM chief executive Rick Wagoner told reporters: "We're sorry to be asking for this support. We wish the market conditions were better. They're not."

Chrysler CEO Bob Nardelli said stakes were incredibly high.

Mr Wagoner, Mr Nardelli and Ford CEO Alan Mulally all arrived by car today after they were widely criticised for travelling to the first hearing to ask for more money by private jet.

On Tuesday, the big three delivered their plans to Capitol Hill and bluntly laid out their future prospects.

Both GM and Chrysler said they needed an immediate infusion of cash in order to last until the end of the year.

Chrysler said it would need $7bn (£4.7bn) by the end of the year just to keep running, and GM asked for $4bn (£2.7bn) immediately as the first instalment of a $12bn (£8.1bn) loan.

GM also asked for a $6bn (£4bn) line of credit to help it survive if economic conditions get worse.

Ford asked for $9bn (£6.1bn) as a "standby line of credit", but said it would not need it unless one of the other big three collapsed, denting confidence in the market even further.

Earlier this week, figures showed industry-wide sales plunged in November by 35%, compared with the same month in 2007.

GM's sales dropped 41%, Ford's fell 30% and Toyota was down 34%.

The big three have warned that bankruptcy could cost millions of jobs and insisted their recoveries, which primarily involve a shift to more fuel-efficient vehicles, had been well under way before the financial crisis struck.

Both GM and Chrysler said the US would face the prospect of shuttered factories and millions of job losses unless the Congress acted quickly.

Mr Mulally and Mr Wagoner both said they would work for one dollar (68p) per year, something Mr Nardelli already does, if their firms took any government loan money.

Ford also offered to cancel management bonuses and salaried employees' merit rises next year, and GM said it would slash top executives' pay. Both said they would sell their corporate aircraft.

All three plans envision the government getting a stake in the car companies that would allow taxpayers to share in future gains if they recover.

Senator Chris Dodd, chairman of the Senate Banking Committee which was hearing from the executives today, said the car manufacturers still needed to prove they could survive and become profitable.

In his opening statement today, Mr Dodd said inaction would only "add more uncertainty and instability to the economy".

Tomorrow, the House Financial Services Committee will hold a similar session.

Mr Dodd said if the problem was simply one of carmakers failing to adapt to global competition, "I'd let them fail".

But such an approach would amount to playing "Russian roulette with the economy of the United States", he added.

He also said he thought the car manufacturers had made a better case for federal assistance than the financial industry, which has already benefited from a $700bn dollar (£478bn) rescue plan.

"In just two weeks' time, the clouds on the economic horizon have grown even darker and greater in number," he said, referring to the time since the last hearing.

"Inaction is no solution."

He also complained that the Bush administration was not tapping into the already-enacted financial rescue package to help the car industry.

"Congress has already given the Bush administration the authority to stabilise this industry," Mr Dodd said.

The Connecticut Democrat warned that the collapse of the US car industry "would affect virtually every sector of our economy"

"Let us be clear this morning," he said. "In my view we need to act."

But Richard Shelby, the top Republican on the Senate's Banking Committee, said he still opposed any bailout for the US car industry.

He suggested a forced restructuring under bankruptcy protection may be the best option.

Mr Shelby cited the fact that the companies have increased their request from $23bn (£17bn) to $34bn (£23 billion) in just two weeks as evidence that this plea was only "the beginning".

The Alabama Republican pressed the carmakers to explain to Congress why such aid would not simply "prop up a failed business model for a few months ... and how are you going to pay it back to the taxpayers?"

US Treasury Secretary Hank Paulson has said the 700 billion- dollar rescue plan was intended only to be used for the financial industry.

But Gene L Dodaro, the top official at the Congress's watchdog agency - the Government Accountability Office - agreed with Mr Dodd that the package set up in October was "worded broadly enough" to permit it to be tapped for the carmakers.

Mr Dodaro said the Federal Reserve also had the authority under existing law to make loans to the domestic car industry if it was to choose to do so.

Mr Dodd said that both Mr Paulson and Fed Chairman Ben Bernanke had been invited to testify at the hearing, but had declined.

GM chief Mr Wagoner told the Senate Banking Committee: "We made mistakes, which we're learning from."

Ford chief executive Mr Mulally also acknowledged mistakes, saying his company's mantra once was "You build it, they will come."

"We produced more vehicles than our customers wanted, then slashed prices," he said.

But as a result of these past mistakes, "we are really focused", he said.

Chrysler chief executive Mr Nardelli promised that his company, recipient of a previous government-subsidised rescue loan in the 1970s which it repaid, would repay taxpayers by 2012 and would devote itself to manufacturing "fuel-efficient cars and trucks that people want to buy".

United Auto Workers union president Ron Gettelfinger told the committee: "We are prepared to do our part."

But he also said workers for the car companies should not have to make disproportionate sacrifices.

He added that any kind of bankruptcy, even a pre-packaged one, was not "a viable option".

Mr Gettelfinger claimed consumers would not buy cars from bankrupt companies, no matter what the terms of the bankruptcy.

Earlier, Senate Majority Leader Harry Reid said prospects for Congress to act this year seemed slim.

"I just don't think we have the votes to do that now," he said.

In the streets outside the Capitol, all three companies were showcasing their futuristic, environmentally-friendly models in the hope of counteracting their image as purveyors of gas-guzzling SUVs.

The three executives made the 520-mile trip from Detroit in hybrid cars - a nod to stinging criticism from members of Congress for making their last trip in corporate jets.

Later, it was revealed that Congressional budget analysts have privately told top Democrats that tapping the 700 billion dollar (£478 billion) rescue programme would not come close to covering the $34bn (£23.1bn) that carmakers now say they need to survive.

It would yield only $10bn (£6.8bn) to $15bn (£10.2bn) in short-term loans, the analysts claimed, according to congressional officials.

All three executives agreed that a multibillion-dollar deal would include a supervisory government board which could order major restructuring of the companies if deemed necessary for survival.

Senator Mike Crapo, an Idaho Republican, said such an oversight board would be "basically a federal restructuring trustee" with some of the same powers as a bankruptcy court.

All three agreed, but Ford chief Mr Mulally added: "I probably need to think about that a little bit. It sounds right, but I just don't know all of the implications of that."