In the UK when we talk of Parliament we tend to be referring to the House of Commons (the lower house), as this is the legislative center of power and thus works easier as a form of short hand in most cases. Although technically parliament refers to both the houses of Westminster - the lords and the commons. ....
As in the US where, technically Congress consists of the Senate and the House of Representatives, but most people when they say "Congress" are referring solely to the House of Representatives.

