Johnson was born in Northwich, Cheshire. After returning from wartime service in the Navy her father, Eric Johnson, founded the Eric Johnson Electrical engineering (electricians) company in Little Leigh near Northwich, Cheshire (now continued by his son).
She passed the Eleven plus and attended the Northwich County Grammar School for Girls (later the County High School Leftwich). At sixth form she level she studied at Sir John Deane"s College from 1982-1984 where she studied History, English and Economics. She gained an Bachelor of Laws in Law from Brunel University.
Johnson is a barrister and was a councillor in the London Borough of Tower Hamlets from 1994 to 2002, serving as Chair of social services. She became a barrister in 1991. From 1999–2005, she was a Barrister in Law at Paddington Law Centre.
She stood unsuccessfully in Brentwood and Ongar at the 2001 general election.
She did not stand for re-election in 2004. She is Hull"s first female Member of Parliament. In November 2005 Johnson was appointed as a Parliamentary Private Secretary to the Minister of State for Pensions Reform, Stephen Timms.
In 2007 she left this role to become an assistant Government Whip. She took on the additional role of Parliamentary Under Secretary of State for Schools in the reshuffle of June 2009.
During the scandal of MPs" expenses it was revealed that Johnson had claimed £987 in architects fees for her second home, which she voluntarily repaid, and had a £563 claim for crockery rejected as "excessive"
In the 2010 general election Johnson polled 39.2% of the vote and held onto the Hull North constituency for Labour with her majority reduced to 641 votes.
In 2014 Johnson proposed a Bill under the Ten Minute Rule that would require sex and relationships education, including discussions around issues such as consent, to be made a compulsory part of the National Curriculum
Selected for the seat in February 2004.
54th United Kingdom Parliament. 55th United Kingdom Parliament. 56th United Kingdom Parliament]
She became a member of the London Assembly on 1 March 2003 after the resignation of Trevor Phillips who became chair of the Commission for Racial Equality, having been next on the list of London-wide members at the 2000 election.
At the May 2005 general election, she was elected Labour Member of Parliament for the Kingston upon Hull North constituency, succeeding veteran Labour Member of Parliament Kevin McNamara.
