Vicky Pryce said she was "feeling just fine" at Parliament, after being convicted for swapping speeding points with ex-Eastleigh MP Chris Huhne.
The electronic tag she has to wear after being released from prison two months into her eight month sentence was not visible.
Ms Pryce, the former head of the economic government service, was at Westminster to give evidence to a House of Lords committee inquiry into the eurozone crisis.
When asked how it felt to be back in government, she said: "I'm feeling just fine, thank you very much."
She announced on her release that she would release a book on her experiences titled 'Prisonomics'.
In contrast, her ex-husband Chris Huhne resigned from the Cabinet and as a Liberal Democrat.
More top news
Increasingly cloudy with drizzly rain tonight. A cloudy start on Monday but brightening up with plenty of sunny spells in the afternoon.
The grass pollen risk will rise to high during warm, dry weather.
Cloudy with patchy rain and drizzle this evening. Mild tonight, then dry with plenty of sunny spells tomorrow.