[3][4] He was previously a special adviser to Chancellor of the Exchequer George Osborne from 2012 to 2016 and Theresa May during her tenure as Prime Minister.

He was educated at All Saints High School and Greenhead College, both in Huddersfield, before studying philosophy, politics and economics at Christ Church, Oxford.

[5] Prior to entering politics, O'Brien conducted outreach work with homeless people and was a chair of school governors.

[5] He was appointed director of the centre-right Policy Exchange in August 2008, succeeding Anthony Browne and Nick Boles in this role.

[12] Subsequently, O'Brien was made a special adviser to Theresa May on the economy and industrial strategy upon her appointment as Prime Minister of the United Kingdom.

Between August 2018 and July 2019, O'Brien was Parliamentary Private Secretary (PPS) to ministers at the Department for Business, Energy and Industrial Strategy.

He was subsequently banned from entering China, Hong Kong and Macau, and Chinese citizens and institutions are prohibited from doing business with him.

[32] On 17 September 2021, O'Brien was appointed Parliamentary Under-Secretary of State at the Department for Levelling Up, Housing and Communities, during the second cabinet reshuffle of the second Johnson ministry.

[47] The report argued for tax reductions and radically more generous capital allowances to boost investment and tackle Britain's productivity problem.

It argued for "bottom up growth" and more generous work allowances in Universal Credit to boost the incomes of low earners and increase employment.

The same month, he published a research note on prolific criminals, drawing on answers obtained from a series of Parliamentary Questions.

The research note, "Super Prolific Criminals, The Case For Action",[50] highlighted that roughly half of all crime in England and Wales is committed by just 10% of offenders.