And even if investigators intercept a Skype call by tapping a suspect's internet connection, its strong encryption means they are likely to be able to determine only the time and the duration of the call.

ECONOMIST: Internet wiretapping

The Police Superintendents' Association, which has been examining the Dutch system, will call on the home secretary at its annual conference later this month to change the law to allow intercept evidence to be used as evidence in British courts.

BBC: NEWS | UK | UK could ring changes on phone taps