Undercover policing laws are ambiguous to the point where ordinary people are at risk of having their private lives infiltrated, an influential group of MPs has warned.
An interim report by the Home Affairs Select Committee says there is an "alarming level of inconsistency" among ministers and senior police officers over the limits of the law.
The issue came to light in 2011 after it was revealed that undercover police officer Pc Mark Kennedy had had sexual relations with women in the environmental group he was trying to infiltrate.
It was later revealed that some undercover police officers used dead children's identities to build cover stories, a practice described as "ghoulish" in the MPs' report.
More top news
Thousands of people have linked hands on Westminster Bridge in a show of solidarity - one week after the terror attack in the capital.
PC Keith Palmer, 48, stabbed by Khalid Masood while on duty in the grounds of the Palace of Westminster last Wednesday.
Engineering firm CH2M won the £170 million contract but have pulled out of phase two of the project over alleged conflicts of interest.