Oscar Árias, the Costa Rican former president and Nobel peace prize laureate, has been enveloped in scandal after a sexual assault complaint was brought against him by a nuclear disarmament activist.

Árias denied the allegation, saying he has never acted against the will of any woman and has fought for gender equality during his career.

Árias was president of Costa Rica from 1986 to 1990 and again from 2006 to 2010. He was awarded the Nobel peace prize in 1987 for his efforts to end civil wars in Central America.

According to the publication Semanario Universidad, the woman said the incident took place 1 December 2014, at the ex-president’s home in the capital, San José, where she had come for a meeting related to her cause.

She told the publication that Árias grabbed her from behind, touched her breasts, began to kiss her and penetrated her with his fingers, while she reminded him that he was a married man.

“I do not remember well what he replied to me, but he continued to touch me,” the woman was quoted as saying. “Then he told me to wait a bit and he left the office. I didn’t know what to do. I felt trapped in that moment.”

Semanario Universidad posted a partial image of the criminal complaint filed on Monday afternoon that names the suspected crime as rape.

Responding to an Associated Press request for comment, the prosecutor’s office acknowledged receiving “a complaint against a person with the last name Arias for a presumed sexual crime”, but said it was prevented by law from releasing more information.

According to Semanario Universidad, the woman – who was then 30 – said Arias proposed meeting elsewhere, and she used that as an excuse to leave, later telling him she had gone to a meeting with an adviser to a then lawmaker. She asked them to let her go to the national assembly building for fear the word would get back to Arias if she did not.

The lawmaker and the adviser confirmed to Semanario Universidad that the activist had told them about the alleged incident and was visibly upset.

“I have never acted in disrespect of the will of any woman, much less in the case of their freedom to relate with another person,” Arias said in a brief statement. “In my public life I have promoted gender equality since I consider it an indispensable means to achieve a more just and equitable society for all people.”

The statement added that since there was a complaint against him, he would have no further public comment and would mount his defense in court.