EU rules do not stop national authorities carrying out language tests on foreign doctors working in the UK, the European Commission said.
A spokesman was responding to a Health Select Committee report calling for tighter vetting of foreign doctors, including rapid improvements to the way English language competency is checked among GPs who travel to the UK for work.
It urged ministers to press for EU rule changes to allow checks by the General Medical Council.
The Commission said foreign doctors working in the UK were covered by EU laws providing for the mutual recognition of professional qualifications across borders.
That included doctors setting up permanently in the UK and those staying for a limited time to provide temporary shift cover.
"In both cases, linguistic requirements apply, so once a doctor is authorised to work in the UK they have to have the right knowledge of English to do their job properly," said the spokesman.
The level of knowledge of English depended on the specific medical job - with more stringent requirements for doctors working directly with the public than for those based in a laboratory and not in professional contact with the public.
"The Professional Qualifications Directive says that language requirements can be imposed, but they need to be proportionate and on a case-by-case basis.
"The competent authority cannot impose a general test regardless of a doctor's situation; they have to give the doctor an opportunity to demonstrate their level of English."
That, explained the spokesman, could mean providing proof of language qualifications, or "coming in for a chat".
But, ultimately, a visiting doctor could be subjected to a language test.
"If the competent authority is not convinced that the doctor has the right level of English they can then impose a language test.
"So the EU Directive does not forbid the competent authority from imposing tests in such circumstances."
The committee's report follows an outcry over the death of a patient, David Gray, who was given 10 times the correct dose of morphine by a German locum, Daniel Ubani.
In February this year a coroner delivered a verdict of unlawful killing.
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.
Dr Ubani's poor English meant he was refused work by the NHS in West Yorkshire but was later accepted in Cornwall.
In evidence to the committee last month, the General Medical Council's (GMC) chief executive, Niall Dickson, said there was a "gaping hole" in the registration system for doctors coming from the European Economic Area (EEA).
Even though it regulates doctors, the GMC is prevented by law from checking the language skills of medics or fully assessing their competency.
The committee heard there was difference of opinion between the GMC and the Government on whether the law could be amended without facing sanctions from Europe.
Its report said: "If the GMC had been able to check the language skills and clinical competence of EEA doctors wishing to practise as GPs, lives might have been saved.
"There is a difference of legal opinion between the Department of Health and the GMC.
"We recommend that, without delay, the Department and the Council share their legal advice about the legality of amending the Medical Act 1983."