A former clinical director of cancer services at a Welsh hospital says he took up a post in England because he was frustrated with the NHS in Wales.
Prof Leonard criticised the provision of scanning equipment in Swansea
Professor Robert Leonard said cancer services in Swansea have been left under-resourced.
Swansea NHS Trust said it understood the points he had made and agreed its cancer services needed investment.
The assembly government said tackling cancer remained one of its "top health priorities".
Prof Leonard was the clinical director of cancer services at Swansea NHS Trust, as well as the director of the South West Wales Cancer Institute.
He left his job in August to join a hospital trust in London.
He told Radio Wales he was not critical of Swansea NHS Trust because he believed people there were doing their best under the circumstances, but said he thought it was time for an honest debate in Wales on some NHS issues.
On the clinical side, he said he was disappointed with the lack of an MRI scanner, which he described as "basic kit in most places," at Swansea's Singleton Hospital.
He said he believed Swansea suffered from a lack of scanning equipment and problems with access to radiotherapy treatment.
He said there was around a six-week wait in Swansea for radical radiotherapy treatment, whereas it was down to around two to three weeks in west London where he now works.
Prof Leonard told Radio Wales: "I don't think it is possible in the circumstances we were working in Swansea, to get it much below where we were, because you've only got two or three functioning machines, you've got a big population of patients, you've got overworked radiotherapy oncologists."
The specialist also said he believed that too many resources were pumped into medical research in Cardiff, instead of elsewhere in Wales.
He added: "There's this constant attempt to smother the development of a healthy, vibrant teaching environment in medicine outside of the capital, which is not good for anybody.
"I don't think Cardiff gains from it and I'm sure Swansea doesn't gain from it."
Swansea NHS Trust said it agreed that the trust required investment.
An assembly government spokesman said: "As part of the All-Wales Modernisation Programme which has been established, we are currently ensuring that radiotherapy equipment, MRI and CT Scanners are up to date and their capacity increased in line with commissioning plans to reduce patients' waits.
"As part of our capital investment programme we have also increased funding for linear accelerators.
"Cancer research receives a disproportionately large amount of funding, from the Wales Office of Research and Development for Health and Social Care (WORD) compared with other disease areas."