German Chancellor Angela Merkel has said US and British spying "sows distrust" among allies.
She used her inaugural address to parliament after her re-election to warn that such surveillance ultimately undermined mutual security.
She also accused the UK and US of using spy agencies to gain economic advantage rather than just for security.
In October, Germany summoned the US ambassador over claims that the US monitored Mrs Merkel's mobile.
The chancellor at that time demanded a "complete explanation" of the claims, which were made in news magazine Der Spiegel.
The magazine based its stories on material from Edward Snowden, a former contractor for the US National Security Agency (NSA).
The White House said when the allegations emerged that it was not monitoring her calls and would not do so in future.
However, it left open the question of whether calls had been listened to in the past.
In a separate development on Wednesday, US spy chief James Clapper said that Mr Snowden's leaks had severely damaged America's national security apparatus.
Mr Clapper told a hearing of the Senate Intelligence Committee that the leaks have aided America's adversaries and undermined co-operation with foreign partners.
"What Snowden has stolen and exposed has gone way, way beyond his professed concerns with so-called domestic surveillance programmes," he said.
"As a result, we've lost critical foreign intelligence collection sources, including some shared with us by valued partners."
Mr Clapper has been accused of lying at an earlier Congress hearing over the extent of the NSA's surveillance activity.
Earlier this week a group of congressmen was pushing for him to be fired over the issue.
In the first major speech of her third term, after winning September's election, Mrs Merkel said nobody doubted that intelligence agencies had helped to protect the German people from terrorism and crime.
"But does that make it right for our closest allies, like the United States or Britain, to access all imaginable data - arguing that it helps their own security and that of their partners," she said.
"Can it be right that it's not just about defending against terrorist threats but also to gain advantage over their allies, for example, in negotiations at G20 summits or UN sessions?
"Our answer can only be: 'No, that cannot be right.'"
She warned that succumbing to the temptation to "do everything that is technically doable" led to mistrust between allies.
However, she emphasised that the "transatlantic partnership remains of outstanding importance".
But she conceded that the allies remain "far apart" on the "ethical question" of freedom versus security in state surveillance.
State-monitoring of phone calls has a particular resonance in Germany. Mrs Merkel grew up in East Germany, where phone-tapping was pervasive.