David Cameron "silently acquiesced" to an EU statement raising questions about mass US surveillance operations and Britain's collaboration in them, Angela Merkel said on Friday following a two-day Brussels summit.

All 28 national leaders, Cameron included, responded to allegations of US tapping of the German chancellor's mobile phone and large-scale interception of telephone calls in France by voicing concern about the US National Security Agency (NSA) and deploring the possible collapse of transatlantic trust unleashed by the ongoing revelations. The statement also implicitly questioned Britain's role through the activities of the GCHQ.

Asked whether the prime minister supported the statement cobbled together during a two-hour debate on the intelligence row, Merkel said: "David Cameron was present at the discussion. He listened to it. He wasn't against it. That is silent acquiescence as far as I go."

Another European leader confirmed Merkel's account of events, while a senior EU official present at the discussion said: "Britain was almost not intervening in the debate. It agreed immediately."

The leaders, including the prime minister, agreed that the NSA revelations raised "deep concerns among European citizens" and that a resulting loss of trust could imperil the transatlantic effort to combat terrorism.

In a pointed reference to GCHQ's role, the leaders' statement said the issue of trust applied not only to the US, but also to relations between EU member states.

"Intelligence gathering is a vital element in the fight against terrorism. This applies to relations between European countries as well as to relations with the US. A lack of trust could prejudice the necessary co-operation in the field of intelligence gathering."

At a post-summit press conference, the PM repeatedly insisted he would not discuss issues pertaining to national security or intelligence gathering, but described the agreed statement as sensible, and aimed at averting a breach between the EU and the US.

"The leaders of the European Union issued a good and sensible statement about this matter and I agree with that statement," he said.

Shaken by recent revelations about NSA operations in France and Germany, EU leaders and Merkel in particular warned the international fight against terrorism was jeopardised by the perception that mass US surveillance was out of control.

Merkel drove the point home: "We need trust among allies and partners. Such trust now has to be built anew … The United States of America and Europe face common challenges. We are allies. But such an alliance can only be built on trust."

While European leaders warned that the mass surveillance imperilled the counter-terrorism effort, Cameron blamed the US whistleblower, Edward Snowden, as well as "the newspapers helping him".

In what was seen as his most trenchant attack on the Guardian, the PM said: "What Mr Snowden has in effect done and what some newspapers are assisting him in doing is going to make it a lot more difficult to keep our countries and our citizens safe.

"There are lots of people who want to do us harm, who want to blow up our families, who want to maim people in our countries. That is a fact, it's a not a pleasant fact, but it's true … That is the threat that we face.

"The point is what Snowden is doing and to an extent what the newspapers are doing in helping him do what he is doing, is frankly signalling to people who mean to do us harm how to evade and avoid intelligence and surveillance and other techniques. That is not going to make our world safer. It's going to make our world more dangerous. The first priority of a prime minister is to help try and keep your country safe. That means not having some lah-di-dah, airy-fairy view about what this all means."

The leaders agreed that Germany and France are to spearhead a drive to try to force Washington to agree new transatlantic rules on intelligence and security service behaviour in the wake of the Snowden revelations.

François Hollande also called for a new code of conduct agreed between national intelligence services in the EU, begging the question of whether Britain would opt to join in.

The Franco-German talks with the US were open for others to join, the summit agreed. British officials made plain the UK would not take part. Cameron said that Barack Obama would welcome the talks with the Europeans, but set Britain apart.

"Obviously Britain has a very strong and unique intelligence relationship with the US," he said.

Part of that is the so-called Anglophone Five Eyes pact on intelligence-sharing between the US, UK, Canada, Australia and New Zealand. Given Britain is the sole EU member of the pact, it surfaced as a source of rancour and envy in the debate. According to another senior official who witnessed the two-hour discussion on intelligence snooping, Merkel raised the issue directly with Cameron in private.

"Regarding Britain, there were some allusions about the so-called Five Eyes," the official said.

"Angela Merkel and others said that 'unlike David we are unfortunately not part of it'. David Cameron then made the point about the importance that the group has for British national security and also the fight against terrorism. He gave figures about how many terrorist attacks and how many casualties were avoided in the last years since he was prime minister."

The private discussion highlighted the divergent views of Cameron and other European leaders on the NSA controversy. While most leaders deplored the reports of Merkel's phone being tapped, Cameron declined to join them.

Merkel told the meeting that the issue was not her mobile, but "the phones of millions of European citizens".

Hollande dismissed the argument that spies will be spies. "He said that some people ask: 'Why are you attacking the Americans? Everybody does this.' But that is not true, at this level of spying, I don't how many millions of millions of citizens," the source said. "It raises issues of privacy and fundamental rights."

It was plain that France and Germany both want to limit the damage from the NSA furore, but also hope to engage the US to rein in its activities. They set a deadline of the end of the year for results. Senior officials said the big fear was of further Snowden revelations upsetting their agenda to get transatlantic relations back on an even keel.

Merkel briefed the other leaders in some detail on her 20-minute conversation with Obama on Wednesday. Several participants commented that they thought the US leader was embarrassed, the sources said.

The European anger and frustration was directed at a US agency seen to be out of control and beyond appropriate scrutiny, rather than being aimed at Obama.