German chancellor in first meeting with president since revelation that US intelligence services tapped her mobile phone

Angela Merkel should ask Barack Obama to destroy her NSA file when she meets the American president in Washington this week, a leading German opposition politician has told the Guardian.

The Greens warn that failure to address the intelligence monitor scandal would risk undermining the credibility of the western alliance during the Ukraine crisis.

"Close co-operation between western allies requires joint values – also in relation to the activities of our intelligence services," said Omid Nouripour, the Green party's foreign policy spokesperson.

"Trying to sit out the NSA scandal won't work: we can't afford to let the remaining open questions strain relations during on the current crisis," he said, suggesting that a symbolic act, such as the destruction of Merkel's NSA file, could help to mend US-German relations.

The German chancellor travels to the US on Thursday and will meet Obama on Friday.

So far, the US government has refused to allow Merkel access to her NSA file or answer formal questions about its surveillance activities, a recent query to the German Bundestag has shown. According to a report in German magazine Der Spiegel, the NSA kept more than 300 reports on Merkel in a special heads of state databank.

Merkel's office has been eager to lower expectations ahead of the first meeting between the two leaders since it emerged in October that US intelligence services had tapped Merkel's mobile phone.

Her spokesperson, Steffen Seibert, said on Friday one visit would not suffice to clear up remaining questions over NSA surveillance, and therefore "concrete results in this area can't be expected".

In Germany, Merkel's critics accuse her of mismanaging the fallout from the scandal. Having at first tried to brush aside the implications of the information revealed by whistleblower Edward Snowden, the chancellor found herself at the centre of the scandal when her mobile number was discovered on a list monitored by the NSA.

Thomas Oppermann, the Social Democratic party's parliamentary leader, has called on Merkel to seek concrete answers over the NSA affair during her visit.

"I hope that the chancellor's visit to Barack Obama will help bring about an agreement. The USA knows espionage is a crime here. The German judiciary won't just sit back and wait while the NSA continues unrestrained," Oppermann said when Merkel's visit was first announced.

But rather than pushing for a stronger European protection law or a review of the "Safe Harbor" data transfer agreement, Merkel tried to turn the crisis into an opportunity by getting the US to sign a "no spy" agreement and allowing Germany to enter the "five eyes" intelligence partnership between the US, Britain, Canada, Australia and New Zealand.

At the time, German leaders claimed that the US government had offered an anti-spying agreement that would, in the words of Merkel's former chief of staff, Ronald Pofalla, "set a standard for future co-operations, at least among western services".

During last December's visit to Germany by the US national security adviser, Susan Rice, American officials reportedly expressed concerns to their German counterparts that any bilateral anti-spying agreement between the two nations would inevitably trigger similar requests from other countries. "The US is not going to set a precedent," one German official was quoted as saying. When Germany's foreign minister, Frank-Walter Steinmeier, and US secretary of state John Kerry met in February, the talk was merely of a future "cyber dialogue".

Critics say Merkel travels to Washington with no concrete plans to show to German citizens. "Prioritising bilateral negotiations over an EU-wide data protection reform has not only been an act of disloyalty towards the European community, but also a massive miscalculation in terms her own political goals," said Jan Phillipp Albrecht, a German Green MEP.

If Merkel prefers to avoid discussing the NSA scandal with her US counterpart, its aftershocks are still being felt throughout Germany. Big media companies and telecommunications providers have used the revelations as the pretext for attacks on US competitors, with Deutsche Telekom launching an "Email Made in Germany" campaign and the CEO of Axel Springer publishing house criticising "close connections between big US online providers and the US intelligence agencies".

Germany's start-up scene, too, has enjoyed an uplift. The valuation of Hoccer, a social messenger app developed in Berlin, which encrypts chats at both ends of the conversation, tripled after WhatsApp was sold to Facebook in February.

Causes such as net neutrality or open access, for years championed only by "hacktivists", have gone mainstream and fill the pages even of more conservative newspapers such as Frankfurter Allgemeine Zeitung. "In the past, we were laughed at – but now it turns out that some of the most paranoid theories were justified", said Martin Haase, a former officer at the Chaos Computer Club network. So-called Cryptoparties, workshops in which hackers teach you how to encrypt your hard-disk or emails over a beer, have enjoyed a massive rise in interest from younger and older users, he said.

Above all, the Snowden revelations have caused great damage to America's image in Germany, with NSA surveillance frequently employed as the chief argument by Germans expressing sympathy or understanding for Russia's position.

An April survey by public broadcaster ARD showed that only 45% of Germans felt their country should position itself as an integral part of a western alliance, while 49% believed Germany's proper role was as a buffer between the west and Russia.