BANGKOK, Thailand - The president of one of the world's biggest seafood exporters expressed frustration and promised change Tuesday after saying an Associated Press investigation that linked slave-peeled shrimp to his company should be a "wake-up call" to the industry.

Thiraphong Chansiri said Thai Union would spend millions of dollars to end reliance on poorly regulated contractors that have been responsible for much of the abuse. He added that under the current system, it was almost impossible to ensure that supply chains were clean.

Like other exporters in Thailand, his company has for years relied heavily on poor migrants working in factories in the port town of Samut Sakhon to peel, gut, and devein shrimp.

The AP report revealed Monday that many of these laborers are undocumented and can end up being tricked or sold into factories where they are forced to work 16-hour days with no time off and little or no pay for sometimes years at a time. Some end up locked inside. Others are allowed to go out, but only if they leave their children or spouse behind as a guarantee against running away.

Thiraphong said that despite great efforts, Thai Union had been unable to keep labor abuses out of its supply chains. It has tried everything from spot-checks by third-party auditors to regular meetings with external suppliers. But problems keep popping up.

He said Thai Union would exclusively use in-house labor for shrimp processing starting Jan. 1, a change he said would cost the company about $5 million.

"This move will provide us with full oversight of all processing stages and will ensure that all workers, whether migrant or Thai, are in safe, legal employment and are treated fairly and with dignity," Thiraphong said.

On Tuesday, the Global Aquaculture Alliance, which audits companies and offers a Best Aquaculture Practices seal of approval, said it would pull its certification from anyone outsourcing shrimp processing.

AP journalists followed trucks from an abusive factory raided last month to major Thai distributors, including a Thai Union subsidiary.

Thai Union and four other exporters that bought shrimp from the sheds sell to companies globally. Those retailers and restaurant chains widely condemned the practices that led to these conditions, and many said they were launching investigations.

Coles, Red Lobster, Whole Foods, and some other companies said they had been assured by Thai Union that their shipments were clean.

Thai Union said shrimp it purchased from the sheds AP tracked did not go to major U.S. companies, while declining to say where it went. In any case, according to U.S. and U.N. standards, if even a single piece of shrimp coming from a company is tied to forced labor, it taints the entire supply chain.