In November 2019, Lay unsuccessfully applied to succeed Sahra Wagenknecht as co-chairperson of the Die Linke parliamentary group in the Bundestag.

After graduating with a degree in sociology, she first worked as a lecturer at the Free University of Berlin from 1999 to 2000, and as a parliamentary-scientific advisor in the PDS faction of the Landtag of Saxony in Dresden from 2000 to 2003.

She then moved to the Ministry of Consumer Protection, Food and Agriculture as a speechwriter for Renate Künast, the Federal Minister responsible at the time.

Lay was a member of the Landtag of Saxony from 2004 to 2009, deputy leader of the Left Party, and spokesperson for labor market policy.

Since January 2016, Lay has been spokesperson for rent, construction and housing policy for the parliamentary group Die Linke in the Bundestag.

[4] Lay and her parliamentary group colleague Michael Leutert, who was also affected, rejected criminal prosecution as unlawful, citing an expert opinion of the Bundestag's Scientific Service, according to which the Saxon Assembly Act was not valid at the time of the crime due to a formal error and the Federal Act was not applicable to the demonstrators.

[5] On 12 February 2015, the Dresden public prosecutor's office discontinued the proceedings without conditions or payments on the grounds that the guilt appeared to be slight.

[6] On 12 November 2019, Lay unsuccessfully applied to succeed Sahra Wagenknecht as Co-Chairwoman of the Left Parliamentary Group in the Bundestag.

In the run-up to the Göttingen Federal Party Congress 2012, she pleaded together with Katja Kipping, Katharina Schwabedissen, Jan van Aken and Thomas Nord for a "Third Way" beyond the reform-oriented and traditional wing of the left.

Through Lay's proposal, with 10 billion euros annually, the federal government should promote social, non-profit, municipal and cooperative housing construction.

[19] Lay advocates the reintroduction of the housing public benefit, so that developers who are oriented towards the common good can receive tax breaks with investment subsidies if they build affordable rented apartments for this purpose on a permanent basis.

[20] Lay regularly takes part in anti-Nazi protests, including a blockade against the annual Nazi march in Dresden in 2011.

[23] In December 2017, the planned awarding of a prize to Ken Jebsen in Berlin's Babylon cinema caused controversy within the Left Party.

On the initiative of Caren Lay, the executive committee of the Left Party then distanced itself in a motion entitled "Clear Edge against Third Position" in which it "unequivocally dissociated itself from the activities of right-wing populists, nationalists, conspiracy theorists and anti-Semites who want to make right-wing populist patterns of explaining the world and 'transverse front' strategies socially acceptable", and expressed its solidarity with Klaus Lederer.