Foreign doctors must be subjected to thorough English language tests by law, the General Medical Council (GMC) argues.
The medical regulator called for immediate government action to change the law and address the "gaping hole" in the registration system for doctors coming to the UK from Europe.
GMC Chief Executive Niall Dickson has written to health trusts after a report last month criticised the current arrangements following the death of David Gray in Cambridgeshire in 2008.
He was killed by German doctor Daniel Ubani, who administered 10 times the normal dose of diamorphine.
Mr Dickson told MPs investigating the issue that the current arrangements across Europe for checking doctors were unsatisfactory.
The GMC has said it is forced to accept skills competency certificates and qualifications "at face value" and is not allowed by European law to check English language skills.
Mr Dickson told the House of Commons Health Select Committee the GMC needed more powers to check doctors coming from the European Economic Area.
"For them we are not allowed to language test and we are not allowed to competency test."
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