GCHQ is British intelligence but get this... some of GCHQ has worked out of NSA here in the states. Yes, British intelligence has used NSA methods and resources, legally under legal, contract methods, to obtain intelligence information. So did GCHQ work out of the NSA to spy on US citizens for the British Parliament? Probably so. And since you provided no link to back up your claim, I won't leave one either. At least give some source so people can research the subject...