An important role in the process of exercising the controlling function of the Sejm is reserved for the Deputies.

Besides their fundamental right to vote in accordance with their own views, Deputies also enjoy the statutory right to express their opinion and to submit motions, both during the debate in the Chamber as well as during the sittings of the committee; in particular, they may present statements according to the procedure described in the Standing Orders. The Act on the Exercise of the Mandate of a Deputy or Senator provides the Deputies with the right to address the Presidium of the Sejm to have a particular matter examined by the Chamber or one of its committees. They may also ask a committee to deal with particular issues. However, the most important role in the controlling powers of the Deputies is played by interpellations and Deputies' questions as well as questions on current issues. Those are the basic instruments which enable the Deputies to participate in the process of parliamentary control.

It is a Deputy's constitutional right to address the Prime Minister and members of the Council of Ministers with interpellations. According to the Standing Orders, interpellations concern issues of substantial importance and are to be submitted in writing to the Marshal of the Sejm. It is vital that each interpellation contain a short presentation of the case as well as questions resulting from the presented facts which remain in the authority of the addressee. The Standing Orders entitle the Presidium of the Sejm to examine whether a particular interpellation fulfils the aforementioned conditions and to refuse to accept those which do not; the Presidium of the Sejm may also order the striking out of phrases from the interpellations which are incompatible with the Deputy's oath. The Marshal of the Sejm refers the interpellation to its addressee. The latter is obliged to return to the Marshal a written answer within 21 days from the receipt of the interpellation. Subsequently the Marshal sends a duplicate of the reply to the Deputy who submitted the interpellation, and the text of the reply is published in an appendix to the shorthand report from the Sejm's sitting. If the Deputy does not receive a reply in due course or finds it unsatisfactory, he may refer to the Marshal for additional explanations or for the inclusion of the interpellation in the agenda. It is of particular importance that the Sejm may ask the addressee to supplement his reply. In any case, the reply to the interpellation shall be treated as a binding opinion of its author.

Deputies' questions are an instrument of a slightly different character. According to art. 115 of the Constitution, similarly as in the case of interpellations, an answer to a question addressed to the Prime Minister and members of the Council of Ministers shall be furnished within 21 days. The purpose of such a question should be the obtainment of information on the current problems of state policy.

Irrespective of the duty to reply to interpellations and Deputies' questions, the Constitution obligates the Prime Minister and members of the Council of Ministers to furnish answers to questions on current issues raised in the course of each sitting of the Sejm. The aforementioned provision is of particular importance for the implementation of the controlling function of the Sejm. The information so obtained may form the basis for the subsequent activities of the Chamber.

Whereas interpellations and Deputies' questions should be submitted in writing - at least during the first stage of the procedure - the Deputies' questions on current issues are formulated orally and require an immediate reply. The Standing Orders contain the rule that a Deputy is to inform the Presidium of the Sejm about the addressee and the subject of the question 12 hours before the commencement of the sitting. After obtaining the opinion of the Council of Seniors, the Presidium of the Sejm determines the sequence of questions for each of the sittings. The Standing Orders state that the sequence in which the questions are presented should correspond to their importance and immediate interest. Such factors as the order in which the Deputies express their willingness to present questions and the creation of opportunities for Deputies depending on the size of their respective political groups should also be taken into account. As opposed to interpellations, neither the question itself nor the answer to it are subject to discussion. However, additional questions and supplementary answers are admissible.

Furthermore, the role of the Deputies is also to inspire the Constitutional Tribunal to perform its controlling function by adjudicating on conformity to the Constitution, ratified international agreements and statutes of all legal provisions contained in the regulations released by the central organs of the State, that is, the Council of Ministers and the State administration. A relevant application to the Tribunal regarding this type of matters may be made by the Marshal of the Sejm or a group of 50 Deputies.