After working in public relations roles for the Britain Israel Communications and Research Centre and Nestlé, Smeeth became more actively involved in the Labour Party.

She was named as an intelligence source to "strictly protect" by the US embassy in London in a 2009 diplomatic cable published online in 2011.

She served as Personal Private Secretary to Tom Watson, Deputy Leader of the Labour Party, but resigned so she could vote against a second Brexit referendum.

She was elected Parliamentary Chair of the Jewish Labour Movement in April 2019 and served until she lost the contest for the Stoke constituency in 2019.

She then became director of public affairs and campaigns at the Britain Israel Communications and Research Centre (BICOM) in November 2005,[6] leaving in early 2007 to work in PR for Nestlé.

According to the cable Smeeth had supplied intelligence about Prime Minister Gordon Brown's intention to call an election in late 2009, and his subsequent decision against doing so at that time.

[14][15] In June 2016 Smeeth resigned her post as Parliamentary Private Secretary (PPS) to the shadow Northern Ireland and Scotland teams, alongside others, in protest at Jeremy Corbyn's leadership.

[20][21][22] Smeeth later issued a statement that Wadsworth was using "traditional antisemitic slurs to attack me for being part of a 'media conspiracy'" and criticised a lack of response from Corbyn or his office, calling on him to resign.

"[20] Smeeth said that she received 25,000 pieces of abuse during July and August, including 20,000 in the 12-hour period immediately following the incident.

[25][26] However, the Jewish Voice for Labour group contested this,[27] by comparing Smeeth's claim with a study by the Community Service Trust, who monitor anti-Semitic and abusive media content.

[28] The study found that over an entire year (encompassing the 12-hour period of Smeeth's claim of 20,000 cases) only 9,008 original tweets concerning Jews were classified as antagonistic.