(Adds Campbell bill and comments from Boehner, Hochberg)
WASHINGTON, June 25 (Reuters) - The future of the U.S. Export-Import Bank was thrown further into doubt on Wednesday after an influential conservative lawmaker labeled the bank an example of corporate cronyism that benefits multi-nationals at the expense of taxpayers and many small companies.
Tea Party Republicans, led by Texas Representative Jeb Hensarling, have mounted a push to shut down the bank, ahead of a Sept. 30 deadline for Ex-Im's charter to be renewed.
The bank's financing has benefited "some of the largest, richest, most politically connected corporations in the world," like Boeing, General Electric, Bechtel Corp and Caterpillar and it could not continue in its current form, Hensarling said.
"If you're a politically connected bank or company that benefits from Ex-Im, no doubt you would like it continue. After all, it's a sweetheart deal for you," Hensarling, chairman of the House of Representatives Financial Services Committee, said at a hearing to consider the bank's reauthorization.
Ex-Im Chairman Fred Hochberg urged lawmakers to keep the bank open, saying small businesses -- which mainly receive short-term support -- would be the first to feel the pinch.
Some Republicans are pushing for a compromise to reform the bank, but if House Republican leaders decline to bring a renewal of Ex-Im's charter to the floor for a vote, the bank could be forced to close.
Representative Kevin McCarthy, chosen last week for the No. 2 job in the House, wants Ex-Im to shut down. House Speaker John Boehner took a sterner tone on Wednesday on media reports that four officials had been suspended or removed as investigators look into charges of improper gifts and kickbacks.
"Given where the Export-Import Bank is today and given the accounts of what's gone on down there, in terms of kickbacks and other things, it's clearly time for all the members to take a serious look at this," Boehner said.
Ex-Im Inspector General Osvaldo Gratacos said there were a number of ongoing investigations, some involving external people, and he hoped to share some information in coming months.
Hochberg said procedures dealing with misconduct allegations had been tightened and the reports showed "if you are doing any funny business, we are onto you."
FOCUS ON BIG-TICKET LOANS
At the hearing, many lawmakers focused questions on loans to foreign buyers of big-ticket Boeing planes, such as the Dubai-based airlines Emirates, which account for a big chunk of lending.
U.S. carriers such as Delta Air Lines could not get the discounted financing Ex-Im provides to buy U.S.-made planes, said Lee Moak, the president of Air Line Pilots Association International, but foreign state-owned airlines could.
Seeking to address those concerns, Republican John Campbell released a proposal to extend the bank's charter for three years, lower its lending cap by a third and put more limits on lending, especially to foreign state-owned companies.
Democrats on the panel were united in their support for the bank, which they said helps exporters compete in international markets where foreign firms benefit from government export support.
The committee's top Democrat, Maxine Waters, said 200 Democrats had signed up to co-sponsor a bill to reauthorize the bank.
"At one time, programs like the Ex-Im bank were so apolitical that they did not even require a vote. Now policies that create thousands of jobs and increase American competitiveness are under constant attack," Waters said.
Hochberg released a report showing South Korea companies had more medium- and long-term export support than their U.S. counterparts despite a much smaller economy, while Chinese firms had three times more. China also offered more than $20 billion in subsidized loans, most tied to purchases of Chinese goods and services.
(Additional reporting by David Lawder, Susan Cornwell and Emily Stephenson; Editing by Caren Bohan and Leslie Adler)