The 66-year-old chairman of the Korean electronics conglomerate, softened his stance after undergoing intense questioning at a special prosecutor's office, just a day after he had accused the Korean media of spinning lies about Samsung.
Lee said he was "ashamed" and would accept the results of the inquiry, which would conclude its work later this month.
"I feel deeply ashamed before the people for causing this disturbance over the Samsung issue," Lee said.
"I will humbly accept the results of the special probe and do my best not to let this kind of things happen again.
"I should be blamed and held responsible for all these things. This is all due to my carelessness."
On Friday, Lee had rejected all allegations that Samsung had raised millions of dollars of bribery and slush funds and illegally helped transfer control of the group to his son, Lee Jae-Yong.
He had also angrily rejected a suggestion that his group was now being seen by the Korean public as a crime ring, blaming the media that "passed on such things".
However, when asked by journalists, Lee appeared to concede that Samsung might have committed some wrongs.
"Some points, maybe. But not 100 per cent," he said.
Korean investigators have asked Lee Myung-Bak, the Korean president, to extend their mandate until April 23.
Special prosecutors have also investigated whether control of the group was illegally transferred from Lee to his son, who is a senior executive of Samsung Electronics.
Lee's son was questioned in March, but investigators then said there was insufficient evidence to indict him.
Hong Ra-Hee, Lee's wife, who is the director-general of the Samsung Museum of Art, was questioned on Wednesday over claims that the suspected fund was used to buy fine art.
Yun Jung-Sok, spokesman for the special prosecutor, said: "It would be correct to say we are in the wrap-up stage."
In November 2007, Kim Yong-chul, a former lawyer for Samsung, had claimed that the company had a slush fund, that it used regularly to bribe prosecutors and judges.
Samsung wields enormous influence in South Korea and the group's assets are valued at $280bn, with exports at $66bn last year.
Samsung individually accounts for more than 20 per cent of Korea's exports.