A two-day hearing is taking place in Washington to examine the extent of lead contamination in children's toys.
Mattel has blamed the lead paint on a Chinese sub-contractor
It comes after the recall of 21 million mainly Chinese-made toys in recent months over their lead content.
On the first day, members of the Consumer Product Safety Commission (CPSC) asked Congress for its budget to be increased to tackle the problem.
Robert Eckert, boss of toymaker Mattel, which has suffered product recalls, stressed the safety of their products.
The largest US toymaker recalled millions of Chinese-made toys in August and September due to hazards from small powerful magnets and lead paint.
Mattel's Fisher-Price unit recalled about 1.5 million toys because of excessive lead paint on the products based on popular characters from Sesame Street and Dora the Explorer.
If lead is ingested by children it can cause learning disabilities and behavioural problems.
But Mr Eckert, in prepared testimony, stressed the safety of the 800 million products the toymaker and its vendors manufacture every year.
But he acknowledged its Chinese producers had not been monitored closely enough.
He said the company's investigation revealed "that a few vendors, either deliberately or out of carelessness, circumvented our long-established safety standards and procedures".
"These recent lead recalls have been a personal disappointment to me" and also those working at Mattel, he said.
However, it had galvanised the company into action, he added.
Mattell has produced 1.5 million of the 13.2 million toys recalled in the past month.
Meanwhile members of the CPSC urged Congress to pass legislation to give the agency better tools to protect consumers from product safety hazards.
"Our small agency has been ignored by the Congress and the public for way too long," said the CPSC's acting chairman, Nancy Nord.
However she pointed to its success in reaching an agreement with its Chinese counterpart which will see China eliminate the use of lead paint on manufactured toys exported to the US.