The UK intelligence agency GCHQ has developed sophisticated tools to manipulate online polls, spam targets with SMS messages, track people by impersonating spammers and monitor social media postings, according to newly-published documents leaked by NSA whistleblower Edward Snowden.

The documents – which were published on First Look Media with accompanying analysis from Glenn Greenwald – disclose a range of GCHQ "effects" programs aimed at tracking targets, spreading information, and manipulating online debates and statistics.

The disclosure comes the day before the UK parliament is due to begin up to three days' debate on emergency legislation governing British surveillance capabilities. With cross-party support the bill is expected to be voted through this week.

Among the programs revealed in the document are:

• GATEWAY: the "ability to artificially increase traffic to a website".

• CLEAN SWEEP which "masquerade[s] Facebook wall posts for individuals or entire countries".

• SCRAPHEAP CHALLENGE for "perfect spoofing of emails from BlackBerry targets".

• UNDERPASS to "change outcome of online polls".

• SPRING BISHOP to find "private photos of targets on Facebook".

The document also details a range of programs designed to collect and store public postings from Facebook, Twitter, LinkedIn and Google+, and to make automated postings on several of the social networks.

Capabilities to boost views of YouTube videos, or to boost the circulation of particular messages are also detailed.

GCHQ has also, the document suggests, developed capabilities to scan and geolocate the IPs of entire cities at a time.

The document does not detail the legal restrictions on using any of the programs, nor state how often any were deployed. Several of the programs, though, are described as being at "pilot" stage.

GCHQ declined to provide First Look Media with a detailed statement, but told the outlet all its programs were "in accordance with a strict legal and policy framework" with "rigorous oversight".

Greenwald characterised the GCHQ statement as "questionable" in his article.