Officials say disclosures about targeting of Joaquín Almunia was 'not the type of behaviour that we expect from strategic partners'

The latest disclosures from the Snowden files provoked exasperation at the European commission, with officials saying they intended to press the British and American governments for answers about the targeting of one its most senior officials.

Reacting shortly after an EU summit had finished in Brussels, the commission said disclosures about the targeting of Joaquín Almunia, a vice-president with responsibility for competition policy, was "not the type of behaviour that we expect from strategic partners, let alone from our own member states".

A spokesman added: "This piece of news follows a series of other revelations which, as we clearly stated in the past, if proven true, are unacceptable and deserve our strongest condemnation."

In Britain, Sir Malcolm Rifkind, the chair of the parliamentary committee that provides oversight of GCHQ, said he was "disturbed by these allegations." He added he could be "examining them in due course as part of the intelligence and security committee's wider investigation into the interception of communications."

A prominent German MP, Hans-Christian Ströbele, who met Edward Snowden in Moscow in October, told the Guardian it was becoming "increasingly clear that Britain has been more than the US' stooge in this surveillance scandal". He suggested the snooping by GCHQ on German government buildings and embassies was unacceptable.

"Great Britain is not just any country. It is a country that we are supposed to be in a union with. It's incredible for one member of the European Union to spy on another – it's like members of a family spying on each other. The German government will need to raise this with the British government directly and ask tough questions about the victims, and that is the right word, of this affair."

The Liberal Democrats have been inching towards calling for an independent commission to investigate the activities of Britain's spy agencies and the party president, Tim Farron, said that "spying on friendly governments like this is not only bad politics, it is bad foreign policy".

"These nations are our allies and we should work together on issues from terrorism to Iran and climate change," he said. "But we seem to be spying on them in conjunction with the NSA in what seems like an industrial basis."

In its strongest statement yet on the issue, Labour called for the ISC to be given beefed up powers, with Douglas Alexander, shadow foreign secretary, saying it was time for Britain to follow the lead of the US and start a more vigorous debate about surveillance.

"I think we should also consider whether the ISC should be empowered to subpoena and to compel witnesses to appear before them as is the case for the other parliament select committees," he said.

Nicolas Imboden, head of the Geneva-based Ideas Centre, said he believed his work in Africa had been the reason he was targeted. "It's about cotton," he told Der Spiegel. "That is clearly economic espionage and politically motivated." For the past 10 years his group has advised and represented African countries such as Chad, Mali and Benin in their fight against high cotton subsidies in western countries including the US. "This was clearly about them trying to gain advantages during WTO negotiations by illegal means," Imboden told Der Spiegel.

But the strongest condemnation came from one of the groups named in the documents, Médecins du Monde.

Leigh Daynes, UK executive director of the organisation said: "If substantiated, snooping on aid workers would be a shameful waste of taxpayers' money. Our doctors, nurses and midwives are not a threat to national security. We're an independent health charity with over 30 years' experience in delivering impartial care in some of the world's poorest and most dangerous places.

"Our medical professionals, many of whom are volunteers, risk their lives daily in countries like Mali and Somalia, and in and around Syria. There is absolutely no reason for our operations to be secretly monitored. We are also gravely concerned about any breach of doctor-patient confidentiality, which would be an egregious impingement on medical ethics."

Nick Pickles, Director of Big Brother Watch, said it appeared GCHQ has "become a law unto itself". Eric King, head of research at Privacy International, added: "The targeting of the international actors tasked with caring for the most vulnerable people, particularly children, is one of the most distressing revelations yet."

Downing Street has repeatedly refused to comment on the allegations in any detail saying it is not comment on security issues. The Israeli government said it would not comment on leaks.