Prison healthcare services are struggling to cope with severe overcrowding in English and Welsh jails, research shows.
Doctors say they do not have the staff, infrastructure or budget to cope with a rising prison population.
At the end of May the prison population in England and Wales peaked at 80,846 with fewer than 300 cells available for new inmates.
"Unacceptable delays in assessing and treating prisoners are now commonplace, while specialist services designed to deal with mental health and drug addiction are badly stretched to the point of becoming ineffective," says prison doctor Ashok Rayani.
He adds that doctors also find it hard to maintain accurate health records especially as prisoners are routinely transferred between institutions without warning.
Prison doctors worry that emergency overcrowding measures such as keeping prisoners in police cells can harm patients due to poor equipment and facilities to perform even the most basic health assessments.
Clare Jenkins, chairman of the BMA's Civil and Public Services Committee said: "Prison healthcare services have been neglected for many years by successive governments.
"The BMA believes that the prison system is reaching an unprecedented crisis point that requires urgent strategic and financial action from the government."