A senior Toyota Motor Corp executive in the United States had warned in January that the company needed to "come clean" over problems associated with stuck accelerators.

An email from Irv Miller, then Toyota's top U.S. spokesman, was sent five days before the automaker launched a recall for about 2.3 million vehicle to fix the sticky accelerator pedals.

"We are not protecting our customers by keeping this quiet," Miller said in his email. "The time to hide on this one is over. We need to come clean."

A copy of the document was obtained by the news agency Reuters on Thursday. Its release comes as Toyota considers whether to appeal a proposed 16.4 million U.S. dollar safety fine by safety regulators.

Toyota has said it would not comment on Miller's email. "We have publicly acknowledged on several occasions that the company did a poor job of communicating during the period preceding our recent recalls," Toyota said in a statement.

"We have subsequently taken a number of important steps to improve our communications with regulators and customers on safety-related matters to ensure that this does not happen again."

Automakers are legally obligated to tell U.S. safety regulators within five days if they determine that a safety defect exists.