Armstrong was born on 30 November 1945 to Hannah P. Lamb and Ernest Armstrong, a Labour Party politician. She attended Monkwearmouth Grammar School before going on to take a BSc in sociology at West Ham Technical Institute (now the University of East London) and a Diploma in Social Work from the University of Birmingham.[1][2] A former social worker and university lecturer, Armstrong worked for VSO in Kenya before entering politics. She was first elected as Durham County Councillor for Crook North Division in 1985.
She was shortlisted for the vacant Sedgefield constituency in 1983, only to lose out to Tony Blair, who went on to be elected MP. Four years later, at the 1987 general election, she was elected to her father's North West Durham seat on his retirement, increasing his majority by 3,806 to 10,162.[3]
Armstrong was seen as a politician on the right of the Labour Party, and was close politically to her near neighbour Tony Blair and the New Labour agenda. However, she is also a member of the Amicustrades union (formerly MSF).[citation needed] Her union ties helped her gain support in rewriting Clause IV.[4]
In the 1992 general election, Armstrong retained her North West Durham constituency by defeating two future party leaders, Theresa May of the Conservatives, who became Prime Minister in 2016, and Tim Farron of the Liberal Democrats.[5]
Armstrong also faced criticism after government defeats in the Commons over the length of time suspected terrorists could be detained without charge, and incitement to religious hatred provisions in the Prevention of Terrorism Act 2005. Press commentators speculated that in losing these votes through miscalculating government support, and in one instance letting the Prime Minister off the "Whip" because she believed the vote was won, Armstrong's position had become vulnerable.[6] However the rumours that she would resign the post[7] proved unfounded.
Afterwards, Conservative leader David Cameron mocked Armstrong during an exchange with Tony Blair, saying "She must be the first Chief Whip in history to put the Prime Minister in the frame for losing a key vote—which is an interesting career move, to say the least."[8] This was the second time David Cameron had attacked her during Prime Minister's Questions; on his debut as Leader of the Opposition on 7 December 2005, Cameron singled her out by saying, "That's the problem with these exchanges—the chief whip on the Labour side shouting like a child. Is she finished? Are you finished?"[9]
She formally resigned from the government on 27 June 2007 when Tony Blair resigned as Prime Minister, she was succeeded by Ed Miliband the following day. On becoming Prime Minister, Gordon Brown announced Armstrong's appointment as Chair of a Parliamentary Labour Party Manifesto Committee drawing up policy ideas covering children. [citation needed]
She is a member of the Joint Committee on the Draft Domestic Abuse Bill.
On 19 July 2019, Armstrong's North West Durham constituency party voted to expel her from the party after she and 67 other Labour peers published an advert in The Guardian on 17 July claiming that Jeremy Corbyn had “failed the test of leadership” over his handling of antisemitismcomplaints within Labour.[15] However, the vote was non-binding as only the National Executive has the mandate to expel members.[citation needed] She is a member of Labour Friends of Israel.[citation needed]