In her first public remarks, Katia Zatuliveter claimed she had been kept in the dark about why she was being kicked out of the UK. Russian Miss Zatuliveter, 25, has been working for Liberal Democrat back-bencher Mike Hancock for two and a half years.
She was arrested on Thursday morning and is being held at an immigration detention centre.
In an e-mail sent yesterday Ms Zatuliveter said: "I was arrested on Thursday at 7am and was told I would be deported. Nobody explained me why and this is my main concern.
"I was not told about the arrangement of the flight. I am in the process of appealing against the deportation and absolutely sure I will win it if there is justice."
Miss Zatuliveter broke her silence amid concerns in Westminster that an alleged spy had been able to work undetected in the House of Commons for so long.