The European Parliament condemned the US covert drone strikes that have killed thousands of civilians in countries such as Pakistan and Yemen, legal charity Reprieve reported.
534 out of 583 MEPs voted in favour of a resolution which demands that EU Member States "do not perpetrate unlawful targeted killings or facilitate such killings by other states", and calling on them to "oppose and ban practices of extra judicial targeted killings."
According to the resolution:
"drone strikes by a State on the territory of another State without the consent of the latter constitute a violation of international law and of the territorial integrity and sovereignty of that country"
"thousands of civilians have reportedly been killed or seriously injured by drone strikes [but] these figures are difficult to estimate, owing to lack of transparency and obstacles to effective investigation"
"drone strike policies have been documented as causing considerable harm to the daily lives of ordinary civilians in the countries concerned, including deep anxiety and psychological trauma, disruption of economic and social activities and reduced access to education among affected communities."
Following the vote, countries such as the UK and Germany will be put under pressure to reveal their involvement in the US drone programme.
Green MEP and chair of the Parliament's sub-committee on human rights Barbara Lochbihler said: "The European Parliament has today raised serious concerns with the use of military drones and the deaths of thousands of civilians resulting from drone strikes.
"MEPs have delivered a strong rebuke to the practice of targeted aerial killings outside a declared war zone, as well as the use of armed drones in war situations outside of the international legal framework.
"The EU needs to address the legal, ethical and security challenges posed by the increasing use of drones, including the urgent need to secure complete transparency and accountability.
"The resolution also stresses that EU member states should strictly refrain from participating in or facilitating extrajudicial targeted killings, for instance by sharing relevant information with countries such as the US."
Reprieve also lodged a complaint with the International Criminal Court (ICC) concerning the involvement of NATO member states in facilitating strikes in Pakistan.
The complaint highlighted the case of Kareem Khan, whose civilian brother and son were killed in a 2009 strike in the Waziristan area of Pakistan.
Khan, who was incarcerated and tortured just days before he was due to testify before MPs and officials, has met with with Parliamentarians from the UK, Germany and the Netherlands to discuss the impact of drone strikes in the area.
British Conservative member of European Parliament Sajjad Karim thinks more people should follow the example of the anti-drone activist and "provide a public face".
Karim welcomed people to "come and tell your story" as this will push a political debate on drones.
Reprieve wrote a letter to Foreign Secretary William Hague after British ambassador to United States suggested the Pentagon buy British-made Brimstone missile for use in its Reaper drones.
In the letter, Reprieve's executive director Clare Algar urged the government to consider the potential legal and diplomatic consequences of supplying UK-built missiles for use in such strikes.
The UK government has not yet commented on the issue.