Prior to her election as MSP, she worked as a personal assistant to Rachel Squire MP.

As an MSP, she chaired the Parliament's Education Committee, where she used her casting vote to reject the student graduate endowment bill, a Scottish National Party (SNP) flagship policy.

At the 2011 Scottish Parliament election, she lost her seat to Alex Neil of the SNP, one of nine Labour MSPs to lose their constituency seats after holding them since the first election to the Scottish Parliament twelve years earlier.

[2] Following the resignation of sitting MP Eric Joyce (and the controversial and flawed 2013 Labour Party Falkirk candidate selection), in a re-run in which all the previous candidates were excluded on 8 December 2013, Whitefield was selected to contest the Falkirk constituency at the 2015 UK general election.

Following the resignation of Scottish Labour leader Richard Leonard, Whitefield chaired Anas Sarwar's leadership campaign.