Bjerregaard was Education Minister from 27 September to 19 December and again from 13 February 1975 to 22 December 1978. 1973 and from 1975 to 1978 in the Cabinets of Anker Jørgensen I, II and III, and Social Minister from 1979 to 1981 in Anker Jørgensen's fourth cabinet. She was European Commissioner for the Environment from 1994 to 1999 and Minister for Food, Agriculture and Fisheries in the Cabinet of Poul Nyrup Rasmussen IV from 2000 to 2001.
She was a member of the Danish parliament (Folketinget) from 21 September 1971 to 22 January 1995 and from 20 November 2001 until 8 February 2005. She was a minister of various cabinets under Anker Jørgensen, and Poul Nyrup Rasmussen. In the 1970s Bjerregaard's political career really took off. In 1971, she was elected to the Odense City Council where she served just one term and resigned in 1973. In 1971 and 1975-1978 she held the position as minister of education. As minister of education she managed to change the Primary School Act in 1975 with the support from the majority of the other parties. On 5 November 1975 Bjerregaard hired an external chancellor for Roskilde University. Venstre and Conservative People's Party wanted to abolish the university, but thanks to the independent politician, former Conservative People's Party member Hans Jørgen Lembourn, the university was saved. In 1976 she introduced restricted admission at the universities meanwhile secured the protection of minorities. In 1977 Bjerregaard got the law about Erhvervsfaglige Grunduddannelser - EFG (Vocational basic training) approved. With former head of department Erik Ib Schmidt she launched the ambitious, complete education plan U 90 from 1978. After the fall of the Berlin Wall, Ritt changed her stance on EU. After being an opponent for many years, she became chairman The Danish European Movement (Den Danske Europabevægelse).
Bjerregaard won the election for Lord Mayor of Copenhagen for the Social Democrats on 16 November 2005, a position she acquired through a high number of personal votes. During her time as Lord Mayor of Copenhagen, Ritt invited mayors of cities around the world to a summit about the climate in the cities. The summit was a prelude to COP15, which took place in Copenhagen. At the summit, Ritt Bjerregaard wished to discuss what the big cities could do to lower CO2-emissions. The meeting was successful and mayors made a promise to take action.
Four days after Bjerregaard was appointed minister of food in February 2000, the first case of mad cow disease, a dangerous brain disease, occurred. With the ministry Bjerregaard acted fast and consistently. The butchering methods were changed and a ban on risk products was installed. These consistent measures were first not received well, neither by the farmers nor the food industry. Especially the initiative to withdraw certain foods from the retailers was criticised. But later on the industry realized that the measures protected the consumers and created great confidence in Danish food products at the export market. In 2001 Bjerregaard introduced the Smiley system. It made occasion for big discussions but today the system is generally recognized.
Bjerregaard was the European Commissioner for Environment, Nuclear Safety and Civil Protection in the Santer Commission from 1995 to 1999, representing Denmark. She has attended at least one Bilderberg Group meeting on 8–11 June 1995. She has also attended Trilateral Commission meetings in 1992, 1998 and 2002.
She has been involved with various organisations. She was vice-president of both OSCE's Parliamentary Assembly and Socialist International Women (SIW) from 1992 to 1994.
Bjerregaard grew up in Vesterbro in Copenhagen as the daughter of joiner Gudmund Bjerregaard and bookkeeper Rita Bjerregaard. She is the oldest of three siblings. She was hospitalized several times because of narrow and unhealthy conditions, until the family acquired an allotment. She finished her exam from Christianshavn Gymnasium in 1958 and became a modern side student from Statens Kursus til Studentereksamen in 1966.
After getting her teachers' certificate in 1964 from Emdrupborg, she worked as a folkeskole (primary school) teacher until 1970. In the same period she was a consultant for publishing house Gyldendal. In 1971, she became assistant professor at Odense College of Education. She has been married to historian Søren Mørch since 1966.
In her spare time, she is a gardener in her organically-managed manor, mostly growing apples.
Ritt Bjerregaard has written several books during her life, latest being the first volume of her memoirs titled 'Ritt' (2015).
During her time as minister of education in 1978, she stayed in a luxury suite at the Ritz Hotel in Paris during a Unesco conference, and this forced her to step down when it became known. Later on The National Audit Office declared that she had not spent more money than other ministers. This later fueled a debate at the Danish Parliament. She returned to politics again soon hereafter in 1979 as social minister.
In the early 1990s it was revealed she had used her connections within the Social Democratic organisations to get a large flat in Copenhagen, although she rarely used it, living on Funen. She was then forced to step down as parliamentary group leader of the Social Democrats. After a year, the case was dropped by the municipality.
Her main campaign promise for the city council elections of 2005 was to erect 5,000 cheap dwellings for 5,000 kroner (948 USD) rent a month within 5 years, should she be elected Lord Mayor. This would allow an average-earning couple, such as policemen and nurses, to gain access to the expensive housing market in Copenhagen. Economists and other experts criticised the plan for being impossible to implement. As of the summer of 2007, twelve such flats had been built.
On 11 July 2007, Bjerregaard claimed she never promised Copenhageners would get 5,000 cheap dwellings within five years, but merely that she would work for that aim. She claimed many unexpected and legal obstacles had come about, and that the government obstructed the issue. She also expected, however, that the 5,000 flats would be ready within 7–10 years.
Since the November 2005 city elections, three prominent Social Democrats have left their fraction: Winnie Berndtson, Finn Rudaizky and Winnie Larsen-Jensen. In June 2007, long-time city politician Larsen-Jensen claimed:
As a city council member I have experienced four Lord Mayors. Ritt is the most autocratic, absolutist, centralist and undemocratic of all.
In return, Bjerregaard claimed that Larsen-Jensen "suffered personal problems" which could not be commented in public. The opposition, as well of the left-wing fractions, have accused Ritt of a dictatorial conduct and obstructing their insight into political cases.
Ritt Bjerregaard is regarded as one of the four most influential social democrats from the so-called golden generation, the others being Mogens Lykketoft, Svend Auken and Poul Nyrup Rasmussen.
In August 2007, Bjerregaard ordered custom designed furniture for her Lord Mayor office at a price of 850,000 kroner (USD 161,000).