Cervical cancer testing among women in England is at a 10-year low, with 20 per cent not being screened.
Although testing saves 5,000 lives each year in the UK, Jo's Cervical Cancer Trust said many women feel it is unnecessary or do not know the causes, symptoms or how to prevent the disease.
Some women miss or delay tests because of work commitments, while others book time off work because they are too embarrassed to discuss it with their bosses.
Jo's Cervical Cancer Trust - the UK's only dedicated cervical cancer charity - is urging more women to attend screenings.
Robert Music, the trust's director, said: "Every day eight women are diagnosed with cervical cancer and three lives are lost to the disease. Cervical screening can help reduce these numbers.
"The screening programme saves 5,000 lives each year in the UK yet 20% of women are not attending their cervical screening test. The more we can do to stress the importance of this life-saving test the better.
"With such a worrying decline in numbers our campaign is also targeting key cities where uptake is below the national average.
"Adverts urging eligible women to get screened will adorn buses across London, Birmingham, Cardiff, Glasgow and Manchester, reaching a potential 5.5 million people."
Over the last decade the number of women being tested for the cancer has fallen, despite a dramatic rise in 2009 following the death of Big Brother star Jade Goody from the disease.