[7] Following the 2010 general election, as the new Member of Parliament for Clwyd South, Jones took her Parliamentary Oath of Allegiance to the Queen in Welsh; she is fluent in the language.

When making her maiden speech in the House of Commons of the United Kingdom on 9 June 2010 Jones spoke of the historic discrimination faced by speakers of the Welsh language.

In her speech, she compared the ordinary people who campaigned for the Welsh language at times when it had not been fashionable to do so as civil rights activists "in the mould of Mrs Rosa Parks".

[8][9] During her time as MP she returned to the issue in her speeches in the Commons, including on the Welsh television channel S4C[10] and campaigned successfully for Welsh to be used in Parliament at meetings of the Welsh Grand Committee[11] She campaigned on military issues, and used her first appearance at Prime Minister's Questions to support a Royal British Legion campaign against the planned abolition of the Chief Coroner's office, which they argued would have undermined the independence and quality of investigations into military deaths.

[13] She assailed Conservative Justice Secretary Kenneth Clarke over "secret inquests" opposed by military families, provoking a "swipe" at the Royal British Legion from the Minister.

She supported Owen Smith in the failed attempt to replace Jeremy Corbyn in the 2016 Labour leadership election.