Dr Holden, who co-ordinated the first aid operation after the number 30 bus was blown up outside BMA House on 7 July 2005, spoke out after giving evidence to the coroner's inquest.
When the explosion occurred, GPC members were at BMA House and, with other senior BMA doctors, helped patients with severe injuries.
Dr Holden said that when he qualified in 1979, training was broad. 'You could pick and mix jobs and do a range of freelance senior house officer roles and registrar positions before committing to a training pathway. Now you have to commit as soon as you qualify,' he said.
'When I qualified you needed a range of skills, such as managing an unconscious patient and delivering a baby. Now, if for example you choose pathology, you won't necessarily get any experience in managing the unconscious patient.'
Young doctors were being 'trained to fill slots', Dr Holden said. 'The system is designed to staff the health service, not educate the professional.'
Dr Holden also called for GP training to be extended to five years. Opportunities to broaden skill sets through extra rotation no longer exist, he argued. 'After foundation years one and two, doctors should be able to spend an extra year doing different specialties before committing.'
Dr Holden said 48 hours a week may not be enough for junior doctors to develop their skills. He said a working week of 60 hours for doctors aged under 35 is feasible.
Links to the full evidence from the coroner's inquiry: