[5] Following the general election, Trickett was made a parliamentary private secretary (PPS) to Peter Mandelson and worked in the Cabinet office and subsequently the Department of Trade and Industry (DTI).

After leaving the government at the time of Mandelson's fall from grace, Trickett was chair of the Compass pressure group.

[7] He played a significant role in rebelling against the Iraq War and participated in demonstrations against it in London, Wakefield, and Leeds.

He led the demands for a recall of parliament at the time of the Israeli attacks on the Lebanon, and the campaign inside the Commons to amend the Companies Bill to secure public listed companies reporting on 'supply chain issues' in line with the suggestions of a range of non governmental organisations.

[6] In June 2007 he was asked by Gordon Brown to chair the party's manifesto group on housing, a position which he declined to take up.

Following the cabinet reshuffle of 3 October 2008, Trickett became the Parliamentary private secretary to the Prime Minister, Gordon Brown.

[17] In February 2016, a former British National Party candidate was convicted of making an anti-semitic verbal attack upon Trickett.

[18][19] On 27 June 2016 Trickett was appointed as Shadow Lord President of the Council and Campaigns and Elections Director.

[25][26] On 5 April 2020, following the election of Keir Starmer as Leader of the Labour Party, Trickett was asked to stand down from his frontbench roles.

[29][30] In September 2024, Trickett was the only MP from the Labour Party to vote for a parliamentary motion which would block the Labour government's plan to means test the Winter Fuel Payment for pensioners, becoming part of the significant backlash to it, arguing that this reform would lead to a further increase in poverty among pensioners during the coming winter, which he warned would be "extremely difficult for my constituents of all ages".

Trickett had supported the introduction of the payment as a universal benefit to pensioners, by Labour chancellor Gordon Brown in 1997.