MPs can ask Parliamentary Questions of any Department or Minister in the Government, including the Prime Minister. The questions will usually be seeking information or pressing for action from the relevant Department or Minister.

A Minister from the Department that is asked the Parliamentary Question is obliged to answer the question. This means that the Government's ministers have to defend their work, their policies and their decision making process in public. There are usually around 40,000 questions asked each year. Almost all of these are Written Parliamentary Questions, which are submitted and replied to in writing.

Around 3,000 questions are Oral Parliamentary Questions, which MPs may submit to be answered in person by a Minister from the relevant Department in the Chamber of the House of Commons. Oral questions are selected by ballot, using a random computer shuffle.

Departments answer oral questions by rota, except for the Prime Minister, who answers questions at midday every Wednesday while the House is sitting. If oral questions do not get answered in the Chamber, because time ran out, then they are answered in writing.

There are rules governing the content of Parliamentary Questions, which Departments must answer, unless it is ruled too costly to do so (the current limit is £600 for written questions). However, questions can be transferred to a different Department if it is more appropriate to do so.