A woman accusing British comedian Russell Brand of rape has told a London court that his behaviour changed dramatically before the alleged assault, describing him as becoming “monster-like” after initially appearing friendly and approachable.

The woman gave evidence at Southwark Crown Court during Brand’s trial on seven sexual offence charges involving six women. The allegations relate to incidents said to have occurred between 1999 and 2009.

Brand denies all the charges and has pleaded not guilty.

The complainant told jurors she first met Brand at the Labour Party conference in Bournemouth in 1999, before he became widely famous. She said she initially felt comfortable speaking with him and believed he was not pursuing her sexually.

However, she alleged that when they were together in a hotel room, his behaviour changed after he partially undressed and asked her to take photographs of him.

“He just changed suddenly from this… camp, friendly and effeminate to monster-like,” she told the court.

She said she felt frightened and threatened during the alleged encounter. The woman also told jurors that she was left crying and feeling ashamed afterwards, adding that she blamed herself for what she said had happened.

The complainant said she did not report the allegation at the time because she feared she would not be believed and worried about the impact on her professional life.

During cross-examination, Brand’s lawyer questioned why she had agreed to return to the hotel room and why she had not left when she became uncomfortable. She rejected suggestions that she had welcomed sexual advances, saying she had felt safe with him initially.

The court proceedings are continuing, with the defence challenging the allegations. Brand maintains that any sexual contact was consensual.