I am much more worried about the illegal activities of the NSA in general and NSA Menwith Hill in particular than the activities of GCHQ, although what they do is worrying enough (Comment, 21 September). There is a contingent of GCHQ at NSA Menwith Hill. I scanned Malcolm Rifkind's article for any mention of NSA Menwith Hill but nothing. We asked a parliamentary question last year as to when the intelligence and security committee last visited Menwith Hill. We are not allowed to know, but they say they have access to every part of the operations area. If Malcolm Rifkind's committee knew about the extent of the NSA surveillance and intelligence-gathering at Menwith Hill, which they should do if they say they know what goes on there (which is doubtful), where is this in their annual report? I am not convinced this committee has any influence or knows what this unaccountable and secretive base is doing.

Lindis Percy

Co-ordinator, Campaign for the Accountability of American Bases

• Simon Jenkins (Comment, 20 September) exposes the complacency here about extent of the domestic and international espionage carried out jointly by the US and UK intelligence agencies, as revealed by Edward Snowden. He also alludes to the NSA bugging Brazilian oil companies during licence talks. However, there has been almost no coverage about the likely application of the information to give British companies an edge when bidding for foreign contracts. A better use of the intelligence would be if HMRC were to access it to reveal the development of tax avoidance schemes.

George Roussopoulos

Hindhead, Surrey