[1] In October 2015, Warner resigned the Labour whip and became a non-affiliated and then crossbench member of the House of Lords,[2] serving until his retirement in 2024.

"[6] In 2009 he said he was "a paid adviser to the General Healthcare Group" as well as "the chairman of NHS London Development Agency".

[7] He was created a Life Peer on 29 July 1998, taking the title Baron Warner, of Brockley in the London Borough of Lewisham.

In August 2010, Warner was appointed by the Conservative–Liberal Democrat coalition government as a commissioner on the Commission on Funding of Care and Support, which was chaired by Andrew Dilnot.

In June 2014, Warner was appointed as a commissioner to oversee improvements in Birmingham City Council's Children's Social Care services, following a poor review by Professor Julian Le Grand.

[16] In March 2014, Warner wrote an article for The Guardian newspaper suggesting that NHS users should pay £10 a month and £20 for every night in hospital.

[19] He also took up a position with Apax Partners – one of the leading private equity investors in healthcare, according to the Alliance for Lobbying Transparency.