The son of a man who died after being treated by a German doctor with poor English said new rules to make doctors have to prove they can speak the language well enough to treat patients are "a step in the right direction" but more must still be done.
The new legislation comes into force after the General Medical Council (GMC) pushed for stronger language testing following the case of David Gray, who died in Cambridgeshire in 2008. He was killed by German doctor Daniel Ubani who administered 10 times the normal dose of diamorphine.
Appearing on ITV's Daybreak Mr Gray's son, Stuart Gray, said: "You can't function as a doctor if you can't communicate with your patients.
"It's definitely a step in the right direction now the English language test is going to be done at a local level but you've still got the issue of clinical competence testing which hasn't been tightened up.
"So for non-EU doctors - they're tested before they're registered with the GMC, but we've still got this issue where that's not happening. Surely you've got to be clinically competent and communicate in the language."
The GP added: "Non-EU doctors are tested for both clinical competency and language competency before they're registered in the UK, so it can be done. If it can be done for non-EEA why not for EEA. Why not just have the same system for all overseas doctors where they're just tested at the point of registration."
Dr Ubani admitted being exhausted after getting only a couple of hours sleep before starting his shift in the UK, and said he was confused about the difference between drugs used here and in Germany. His poor English meant he was refused work by the NHS in one part of the country but was later accepted in Cornwall.
Dr Gray's brother, Rory Gray, said: "Ubani was actually found in a German court to be a charlatan, so simple clinical competency tests would find that out immediately - whether it's a charlatan or a properly qualified competent doctor."
The new rules were announced in February after several other cases in which foreign doctors were said to have provided sub-standard care.
Those coming to the UK from outside the EU already face strict language tests. But doctors from within the European Economic Area have previously been able to be registered to work in the NHS without being asked if they can speak English properly.