European lawmakers threatened on Tuesday to unpick data-sharing agreements with the United States, reacting furiously to reports that U.S. authorities have accessed emails and other personal data from leading Internet companies.

U.S. officials have confirmed the existence of a huge, secret U.S. Internet spying programme, codenamed PRISM, which according to documents leaked to the Washington Post and Britain's Guardian newspaper has given them access to data from firms such as Google, Facebook and Skype.

The news has forced European governments to explain whether they let Washington spy on their citizens or benefited from snooping that would be illegal at home.

In a heated debate in the European Parliament, lawmakers complained that for a decade they had yielded to U.S. demands for access to European financial and travel data and said it was now time to re-examine the deals and to limit data access.

"We need to step back here and say clearly: mass surveillance is not what we want," said Jan Philipp Albrecht, a German Green lawmaker in charge of overhauling the European Union's outdated data protection laws.

The European Parliament is considering a substantial overhaul of its almost 20-year-old data protection rules, which were cast without the Internet in mind. An initial vote in the European Parliament on the changes has been scheduled for July.

Lawmakers said the EU privacy overhaul and existing transatlantic data-sharing deals - the SWIFT agreement on sharing financial transaction data and an agreement on airline passenger name records - were now in jeopardy.

Grasping the nettle

"It is time we grasped the nettle here and put our minds to ending the programme," said Martin Ehrenhauser, an Austrian independent member of the European Parliament, citing the SWIFT and the airline data agreements.

Both data-sharing deals were agreed between the European Union and the United States after the 9/11 attacks in 2001, though European Parliament members sought at the time to limit the amount of data that could be taken from European databases.

Since then, European officials have also attempted to negotiate an umbrella agreement limiting U.S. access to all types of sensitive European data but without much progress.

Those discussions will continue at a meeting in Ireland on Thursday to be attended by U.S. Attorney General Eric Holder and Rand Beers of the U.S. Department of Homeland Security.

Some members of the European Parliament said they felt cheated after the reports about PRISM.

Sophie in 't Veld, a Dutch liberal, said the PRISM spying programme highlighted not only U.S. failings but also political inertia among European leaders who she said had known about the scale of U.S. data access.

She said she had often pressed the European Commission, the EU's executive arm, on whether EU data protection rules could prevent U.S. authorities from accessing and storing Europeans' data but said her queries had gone unanswered.

British Conservative Timothy Kirkhope urged MEPs to avoid knee-jerk anti-Americanism, saying: "Friends listen most when you talk, and not when you shout," he said.

Separately, the Swiss foreign ministry asked the U.S. Embassy in Bern on Tuesday to clarify the role of Edward Snowden, the man who leaked details of the spying programme, while he was stationed as a diplomat in Geneva.

Snowden, a contractor at the U.S. National Security Agency, told the Guardian that one incident that helped push him to go public over PRISM involved an attempt by U.S. intelligence to recruit a Swiss banker to obtain secret information.

The Swiss foreign ministry said it had taken note of media reports on the matter and had asked for U.S. clarification.

"Switzerland expects members of diplomatic missions in Bern and members of permanent missions in Geneva to respect the laws and regulations of the state where they reside," it said in an emailed statement.