Politically, Coffey was elected as a councillor to the Stockport Metropolitan Borough Council in 1984 and became its Labour group leader 1988-92, stepping down from the council in 1992. She contested the parliamentary seat of Cheadle at the 1987 General Election, and finished in third place, some 25,000 votes behind the sitting Conservative MP Stephen Day. She was selected to contest the Conservative held marginal Stockport constituency at the 1992 General Election and she defeated the sitting Conservative MP Tony Favell by 1,422 and has remained the MP there since.
In her first term in Parliament, Coffey served initially as a member of the trade and industry select committee until she was promoted by Tony Blair to become an Opposition whip in 1995 and became an Opposition health spokeswoman in 1996. When Labour won the 1997 General Election, Coffey was appointed as Parliamentary Private Secretary (PPS) to the Prime Minister Tony Blair. In 1998, she became PPS to the Secretary of State for Work and Pensions Alistair Darling and was his assistant from 2002-6 in his capacity as the Secretary of State for Transport and thereafter as Secretary of State for Trade and Industry.
Following the resignation of Tony Blair as Prime Minister on 27 June 2007, Coffey became Parliamentary Private Secretary to the Chancellor of the Exchequer, Alistair Darling.
Coffey is the chair of the All Party Parliamentary Group for Runaway and Missing Children and Adults. In October 2014, Coffey published an independent landmark report: ‘Real Voices – Child sexual exploitation in Greater Manchester,’ commissioned by the Greater Manchester Police and Crime Commissioner in the wake of the Rochdale child sexual abuse scandal. ‘Real Voices’, which placed interviews with children centre stage, made 43 recommendations.
After the report Coffey launched a successful and historic campaign to banish all references to “child prostitution” from UK legislation. She tabled a series of amendments to the Serious Crime Bill in 2015 to remove all references to child prostitution. She received support from all parties and eventually the government agreed to her proposal and tabled an amendment to substitute all references to child prostitution with child sexual exploitation.
In 2017 Coffey wrote a follow up report: ‘Real Voices –Are they being heard?’ which looked at improvements made by the police and other agencies in tackling child sexual exploitation since 2014. Better training and awareness amongst the police and the public had led to significant increases in reporting offences, identification of victims and offenders and intelligence tip-offs.
As the chair of the APPG, Coffey has chaired a number important parliamentary inquiries including in June 2012 on the risks faced by children missing from home and care and May 2016 into the safeguarding of absent children.
Coffey went on to conduct a high profile campaign against the criminal exploitation of children. She maintained that the grooming process for criminal exploitation was very similar to that used for sexual exploitation of children.
The APPG published a report in July 2017 on children who go missing and are exploited by gangs to sell drugs. Coffey particularly focused on the use of vulnerable children and young people in County Lines drugs operations, where children are groomed by criminals and forced to transport and supply drugs from one area to another.
In January 2018, Coffey conducted an independent survey of all 45 police forces asking if there had been an increase in violence connected to County Lines. Coffey campaigned for the children used and trapped in County Lines to be seen as victims, not criminals and for early interventions by agencies to prevent them becoming embedded in gangs. She also called for more use of the human trafficking and slavery laws, which carry heavy penalties against gangs who use children as drug mules.