Carroll is a former special adviser to Kent Police & Crime Commissioner Ann Barnes.
Carroll co-founded the www.fairfueluk.com campaign, which was 'widely credited with influencing the Government to abandon several successive rises in fuel duty'.
He was also campaign manager for the independent candidate for Kent Police & Crime Commissioner Ann Barnes, who won with a landslide in the November 2012 election. He was special adviser to Barnes from Nov 2012 through to Nov 2013. 
Carroll was guest speaker at the 'Confessions of a SPAD' talk in February 2014. At the talk he provided an insight into his last few months working in Westminster and details regarding his role as a special adviser. 
In 2013 he entered Parliament when he was appointed special adviser to chief secretary to the Treasury Danny Alexander. Carroll left this role after the 2015 general election which led to Alexander losing his seat and the Lib Dems no longer being in government. For his role as special adviser to Alexander, Carroll was paid an annual salary of £75,000. 
Move to lobbying
After the 2015 general election, Carroll and other former spad to Danny Alexander, Will de Peyer, founded Tendo Consulting. Tendo is a lobbying firm that advises 'big businesses on improving their contacts within the Westminster bubble'.
De Peyer and Carroll's new role at Tendo were approved by the Advisory Committee on Business Appointments (ACOBA) on the basis they did not 'draw on privileged information available to [them] as a crown servant' for two years from their last day of service, nor become personally involved in lobbying the UK Government on behalf of the new company or its clients. Also, for two years from their last day of service they must seek confirmation from the committee directly that each individual commission is permissible under the terms of his consultancy before taking it up. 
Carroll also sought permission from ACOBA to accept a commission with the Road Haulage Association, which it approved on the basis Carroll had said he did not intend to lobby government or civil servants directly, and that HM Treasury did not consider there to be a conflict of interest. Carroll took up the appointment in June 2015.
In January 2016, Mr Carroll sought the advice of the committee regarding four commissions with TSB Bank, Tax Incentivised Savings Association, McBee Strategic and the National Defence Medal Campaign. The committee found that these commission were agreeable under the terms permitted under the conditions imposed on his consultancy. 
The committee also permitted Mr Carroll to run a campaign on drugs reform through his consultancy, Tendo consulting. Given that the campaign will not involve any direct lobbying of government and that Carroll had not been involved in the relevant policy areas concerned, the commission saw fit to permit the campaign in February 2016. 
In April 2016, ACOBA advised that both Mr Carroll Will de Peyer were permitted to deliver a short presentation to the Association of British Insurers (ABI) on campaign techniques. Given that the presentation was based on Mr Carroll's campaign experience prior to entering crown service, the committee allowed it under the terms of his original consultancy. 
- Twitter Peter Carroll
- Peter Carroll LinkedIn profile, accessed 19 September 2014. Cite error: Invalid
<ref>tag; name "Carroll" defined multiple times with different content
- Shepwaylibdems Confessions of a SPAD: A Hot Potato Evening for Shepway Lib Dems, accessed 28 October 2014
- Laura Hailstone FairFuelUK’s Peter Carroll moves on to Treasury, Commercial Motor, 11, November, 2013, accessed 19 September 2014.
- Gov.UK Special advisers in post, 30 November 2014, accessed 29 April 2015.
- Mark Leftly Ousted Lib Dem special advisers Peter Carroll and Will de Peyer turn to lobbying Independent, 13 July 2015, accessed 21 July 2015.
- Gov.UK Business Appointments Application: Mr William de Peyer 15 June 2015, accessed 21 July 2015.
- Gov.UK Business Appointments Application: Mr Peter Carroll, 15 June 2015, accessed 21 July 2015.
- Gov.UK Business Appointments Applications: Mr Peter Carroll 8 July 2015, accessed 23 September 2015