Britain unveiled plans for sweeping new surveillance powers on Wednesday, including the ability to find out which websites people visit, measures ministers say are vital to keep the country safe but which critics say are an assault on privacy.

Across the western world, debate about how to protect civil rights while helping agencies operate in the digital age has raged since former US intelligence contractor Edward Snowden leaked details of mass surveillance by British and US spies in 2013.

The draft British bill, watered down from an earlier version dubbed a “snoo-pers’ charter” by critics who prevented it reaching the Parliament, was unpr-ecedented in detailing what spies could do and how they would be monitored, said interior minister Theresa May.

“It will provide the strongest safeguards and world-leading oversight arrangements,” Ms May told the Parliament. “And it will give the men and women of our security and intelligence agencies and our law enforcement agencies... The powers they need to protect our country.”

Ms May said many of the new bill’s measures merely updated existing powers or spelled them out. However, the new proposals planned would require communication service providers (CSPs) to retain customers’ data including their Internet use for a year.

The police and spies access to this would be limited to “Internet connection records” — which websites people had visited but not the particular pages — and not their full web browsing histories, she said.

“An Internet connection record is a record of the communications service that a person has used — not a record of every web page they have accessed,” Ms May said. “It is simply the modern equivalent of an itemised phone bill.”

She also said there would be no ban on encryption and in a concession to privacy groups, there would be a two-tier oversight system with a judge getting the power to veto warrants to intercept suspects’ personal data, a move which could help ensure any new law is not struck down by the European courts.

But many were sceptical.