Opposition politicians have lodged a request with Turkey's Constitutional Court asking it to prevent President Recep Tayyip Erdoğan from making statements that breach electoral rules on presidential impartiality.Earlier this week, the pro-Kurdish Peoples' Democratic Party (HDP) had lodged a complaint with the Supreme Election Board that Erdoğan, one of the founders of the ruling Justice and Development Party (AK Party), had broken restrictions that prohibit the president from becoming involved in party politics. But, the HDP's complaint was rejected by Turkey's election regulator in a unanimous decision.In a statement released on Saturday, the HDP said Ali Ürküt, the HDP co-chairman, and Hülya Çapar Duran, a member of the party's legal committee, had filed suits with the Constitutional Court to ban President Erdoğan from openly supporting any political party, which is prohibited by Turkey's electoral laws. The statement said that the President's comments were "an obstacle to forming a fair, free and equal election environment", accusing Erdoğan of using "citizens' taxes in order to gain votes for a political party."In the run up to the June 7 election, Erdoğan has been giving speeches at opening ceremonies across Turkey, during which he has often promoted the presidential system he wants to see replace Turkey's existing parliamentary system.Related: Turkey's electoral board dismisses HDPtarget="_blank"'>