Sara Hiom, Cancer Research UK's director of early diagnosis, said comparing the UK's breast cancer survival rates with other countries can give a better understanding of what is influencing cancer survival.
She said: "We're beginning to see some important clues now, but while we're closing the survival gap for breast cancer UK women continue to fare worse than in these other countries.
"We know that UK women diagnosed with breast cancer are not routinely given CT scans to check if the disease has spread, which could mean we aren't always accurately staging more advanced disease.
"But we also need to investigate the possibility that fewer women with later stage breast cancer in the UK receive the best treatment for their circumstances."
Lead researcher Dr Sarah Walters, from the London School of Hygiene and Tropical Medicine, said the reasons for low overall survival in the UK and Denmark were different:
In Denmark, women are diagnosed with more advanced disease, but survival at each stage is similar to that in other countries. In the UK, women are diagnosed at a similar stage as elsewhere, but survival is lower than women with the same stage of disease in other countries.
In the UK, we should now investigate whether the treatment of women with later-stage breast cancer meets international standards. There is particular concern that this is not the case, especially for older women.
Fewer women survive breast cancer in the UK than in Australia, Canada, Norway and Sweden, research has shown.
Three year cancer survival is 87 percent to 89 percent in the UK compared with 91 percent to 94 percent in the other four countries, according to new figures published in the British Journal of Cancer
Denmark also lags behind with similar survival rates to the UK. But evidence suggests that, unlike in Britain, this is due to women being diagnosed late.
Women were just as likely to be diagnosed at an early stage in the UK as in the other countries, said the scientists. However, the chances of not dying from breast cancer were lower for women with late-stage disease.
One year after diagnosis, survival for women with early-stage disease was close to 100% in all countries.
Older women with breast cancer and women with more advanced disease may be treated less aggressively in the UK, said the researchers.