Patrick Brown allegedly made sexual advances toward a teenage staffer who was drunk and nearly half his age during his time as a federal MP, according to one of two women whose accusations of sexual misconduct led to his resignation as leader of Ontario's Progressive Conservative Party early Thursday.

In a phone interview with Rosemary Barton, co-host of The National, the older of the two women described an encounter with Brown at a party at his Barrie, Ont., home in 2013.

CBC News has agreed not to identify the woman due to the sexual nature of her complaint, first reported — along with allegations from the other woman — by CTV News late Wednesday. The allegations from both women date back to when Brown was a federal MP in the Barrie area. ​

The woman, who was a 19-year-old summer student at the time, told Barton she was at a party for Hockey Night in Barrie — an annual charity event — where Brown's friend provided her with a series of free alcoholic drinks. The party was at a nightclub, The Bank, that has since closed. Sources tell CBC News Brown frequented the club during his time as a federal MP.

By the time the party moved to Brown's house, the woman asserts she was "very" intoxicated.

Hooligans restaurant in downtown Barrie, Ont., is the former site of the nightclub, called The Bank, where a woman says she was with Brown before he made unwanted sexual advances toward her in 2013. (CBC)

She says Brown invited her into his bedroom and began kissing her. She claims she didn't kiss him back, and instead froze up. Brown stopped kissing her, when she says she told him, "I have a boyfriend and you need to take me home."

She described the encounter with Brown, who was 35 at the time and almost twice her age, as "awkward."

The next morning, she said, she woke up crying. She said she didn't tell anyone what happened immediately because she hoped things would go back to normal. At work that day, she said Brown called her but didn't mention what happened the previous night.

While she remained working for him, the woman said Brown invited her to travel to India with him as his assistant.

She said Brown told her she would look good on an elephant.

She agreed to the trip, she said, because she didn't know how to say no.

Later, the woman said, she "broke down" when she told her father about the incident at Brown's home and the invitation to travel with him to India.

She didn't go on the trip, but said she continued working for Brown while she attended university.

"It was an ideal student job," she said.

The woman's allegations of sexual misconduct stem from when Patrick Brown was a federal MP in Barrie, Ont. (Nathan Denette/Canadian Press)

The following summer she returned to his office and said while she didn't have much contact with him, she remembers feeling "anxious" whenever they interacted.

The woman claims nothing physical ever transpired between them, but he continued to make sexual comments to her.

After Brown launched his bid for leader of the Progressive Conservative Party of Ontario, the woman says he told her he feared not being married would hurt his chances in the race, and alleges he said, "I wish I could find a 26-year-old version of you."

'These allegations are false'

Brown called a snap news conference at the provincial legislature on Wednesday night to deny the allegations, calling them "categorically untrue."

"These allegations are false and have been difficult to hear," said Brown in a statement issued just before 1:30 a.m. ET.

"However, defeating [Ontario Premier] Kathleen Wynne in 2018 is more important than one individual. For this reason, after consulting with caucus, friends and family I have decided to step down as leader of the Ontario PC Party. I will remain on as a MPP while I definitively clear my name from these false allegations."

The allegations and the resignation leave the Ontario PCs in turmoil and without a leader, with the provincial election scheduled for June 7.

Conservatives call for resignation

In an appearance only about a minute long on Wednesday night, a visibly distressed Brown said he had learned about the allegations a couple of hours earlier.

Ontario Progressive Conservative Leader Patrick Brown denied allegations of sexual misconduct at an unexpected news conference at Queen's Park Wednesday night. 1:27

"I want to say: These allegations are false. Every one of them," he said. "I will defend myself as hard as I can, with all the means at my disposal.

"I know that the court of public opinion moves fast. I have instructed my attorneys to ensure that these allegations are addressed where they should be: in a court of law."

Brown stood alone at a podium during the news conference, walked briskly away without taking questions and left in a waiting vehicle.

The pressure on Brown to resign ramped up immediately. His top three campaign staff quit, saying they had urged Brown to step down, but he had refused. Then his caucus members held a conference call, during which MPPs demanded Brown resign.

Patrick Brown left Queen's Park immediately after making his statement early Jan. 25 and refused to take questions. (Aaron Vincent Elkaim/Canadian Press)

"In the interest of the Ontario PC Party we unanimously agree that Mr. Brown cannot continue serving as the Leader," said a statement from the caucus, issued by deputy leaders Sylvia Jones and Steve Clark.

"Mr. Brown is entitled to a legal defence and due process, but he cannot lead us into an election as a result of these allegations."

Makes quick exit without statement after hastily calling press conference to deny misconduct allegations 1:15

Brown won the PC leadership race in 2015. He had served as a Conservative MP on Stephen Harper's backbenches for nine years, and was seen by many as a long-shot candidate. But he built a strong organization and signed up thousands of new members to the party from communities in the Greater Toronto Area that had shown little support for the PCs.

The PCs then enjoyed a wide lead over Wynne's Liberals in nearly all opinion polls throughout 2016 and 2017, while his party out-fundraised the Liberals and the Ontario NDP combined.

Brown launched his campaign platform in November, trying to position the PCs as a centrist party, ready to end 14 years of Liberal reign in Ontario but pledging not to reverse most of the Wynne government's key programs.

The Ontario Progressive Conservative platform for the 2018 election features Patrick Brown prominently on the cover. (Mike Crawley/CBC)

With Brown's face splashed on the cover of the platform, and the election campaign due to begin in early May, the party will be scrambling to get back on track.

It is unclear who will replace Brown and how the new leader will be chosen. The statement issued by the deputy leaders said "caucus will immediately consult with party officials and members on best way to move forward."

'This is, plain and simple, horrible,' says Fedeli. 3:54

The party constitution says when a leader resigns, the caucus must select an interim leader to serve until a leadership convention can be held. Diverting resources toward a snap leadership convention is likely to be the last thing the PCs want to do with an election campaign around the corner.

Some of the names being floated already as potential replacements for Brown include MPPs Lisa MacLeod and Vic Fedeli, who both sought the leadership in 2015, as well as the two deputy leaders, Clark and Jones.