South Dakota legislator Mathew Wollmann, 26, admitted to having sex with two interns in 2015 and 2016

A South Dakota legislator who admitted to having sexual contact with two interns has resigned and says he regrets his actions.

Republican Rep. Mathew Wollmann announced his resignation in a letter on Monday, according to the Mitchell Daily Republic.

The 26-year-old former Marine didn't immediately respond to messages from The Associated Press.

Last week, he said both interns were over age 21 and that the contact which took place in 2015 and 2016, was consensual. But his colleagues had voted to set up a committee to investigate his actions and were scheduled to meet Tuesday.

Majority Leader Lee Qualm told the AP that Wollmann, from the eastern South Dakota city of Madison, informed him in person on Monday that he would resign.

'I have nothing but the greatest respect for those that I have grown so close to these past two years, and even in these early days of the 92nd legislative session,' Wollmann wrote in the letter.

Republican Rep. Mathew Wollmann sits on the House floor in Pierre, SD on Wednesday. The House decided to investigate Wollmann after he admitted to having sexual relations with interns

Video courtesy of KSFY

'Those that read this should know that it is my wrongdoing that has put this institution in a sour light. Those responsible for me have displayed nothing but the highest honor for this establishment.

Qualm, House Speaker Mark Mickelson and Minority Leader Spencer Hawley said in a statement that Wollmann decided 'this was best for him, his fiancé, his family and the young ladies involved.'

'Every legislator has an obligation to refrain from behavior unbecoming to the Legislature and inconsistent with maintaining the public's trust,' the House leaders said.

The 26-year-old former Marine decided to do what was 'best for him, his fiancee, his family and the young ladies involved'

In South Dakota, legislative interns are college students, some 21 or older. Legislative rules don't explicitly ban sexual contact or relationships between lawmakers and interns, although they do prohibit sexual harassment and call on lawmakers to maintain 'the highest of moral and ethical standards.'

Wollmann's public admission came shortly after a legislative committee voted down a new rule — proposed by a lawmaker who had raised questions privately about Wollmann's conduct — to explicitly bar legislators from sexual contact with interns and pages.

One lawmaker who spoke against the change said he felt the current rules were sufficient.

The House leaders said they will meet with lawmakers, interns and staff to discuss potential improvements that could be made to legislator and employee training and any updates to legislative rules. Hawley told the AP that he supports discussing new rules.

Governor Dennis Daugaard said he is acting quickly to replace Wollmann's seat.

Wollmann is the second South Dakota lawmaker in roughly a decade to be investigated for alleged misconduct involving interns or pages.

In 2007, the state Senate censured Democrat Dan Sutton after he was accused of fondling an 18-year-old page when they shared a motel room during the 2006 legislative session. Sutton denied the allegation and was re-elected.