A Conservative MP's chief of staff repeatedly raped a woman in his boss's Palace of Westminster office after calling her a "bitch" when she snubbed his advances, a court was told.

Samuel Armstrong allegedly attacked the woman, said to be in her 20s and also a parliamentary worker, after drinking alcohol in Parliament's Sports and Social Bar.

The 24-year-old, who works for South Thanet MP Craig Mackinlay, is said to have attacked the woman after taking her on a tour of the Houses of Parliament.

Armstrong, from Danbury, Essex, is charged with two counts of rape, one of sexual assault and one of assault by penetration on 14 October 2016.

London's Southwark Crown Court heard that the woman, who was friends with Armstrong, "felt like a hostage during the attack" and was found by a cleaner who called police.

The court heard how Armstrong met the woman at around 8pm at the Houses of Parliament and had drunk alcohol in the bar, then at 9.30pm he took the woman to the roof garden terrace.

The woman remembers having "four or five drinks" and rated herself "a half" drunk on a ten-point scale, reported the Mail Online.

A jury was told that the woman fell asleep in Mackinlay's office and Armstrong began kissing her and asking her back to his flat in Clapham.

"I fell asleep and the next thing I remember was him (Armstrong) with his hand on my left breast, and him kissing my mouth and my neck," she said according to BBC News.

"He kept saying come back to his flat, and I kept mumbling 'no', and he kept saying it. He called me a 'bitch' a few times."

Armstrong then allegedly began taking off her clothes with the woman saying she "froze" and then asked him "What are you doing?".

Prosecutor Mark Heywood QC told the court that Armstrong told her "this is what you want". Heywood said: "In saying that he was not, of course, genuinely speaking for her or reflecting any truth of the situation. He was imposing himself on her."

Heywood added: "His reaction was telling: it was one full of entitlement. He was not prepared to accept any refusal.

"Instead, he became insistent, determined perhaps. As he knew perfectly well, he had her at a very distinct disadvantage."

Armstrong then allegedly got on top of the woman and raped her before forcing himself on her again pushing her "head down as he raped her" in an "unpleasant attack".

Armstrong then allegedly left her there and used another exit before sending her several text messages, asking if she was able to leave the complex ok.

The court heard the alleged victim suffered a number of bruises to her body which were consistent with, but do not prove, the allegations, reported the Mail Online.

Defending Armstrong, Sarah Forshaw QC, suggested the complainant suffered from mental health issues in the past, and the woman confirmed said she was suffering from mild depression and anxiety at the time of the incident.

Forshaw suggested that the woman was "inhibited by drink", found Armstrong attractive and willingly had sex with him.

Armstrong denies the charges. The trial continues.