Hundreds of people rallied in Krakow to protest arrangements for Sunday's burial ceremony, BBC News reports.
Polish film director Andrzej Wajda called the plans "misplaced" and "hastily made."
"Lech Kaczynski was an ordinary and good man but there is no reason for him to lie in the Wawel among the kings of Poland," he wrote in an open letter printed by the Gazeta Wyborcza newspaper.
World leaders including U.S. President Barack Obama, German Chancellor Angela Merkel and the presidents of France and Russia, Nicolas Sarkozy and Dmitry Medvedev, will attend Kaczynski's funeral. The president and his wife died in a plane crash last Saturday in which 94 other people also perished.
The victims included politicians, military leaders, church officials, the country's national bank chief, the head of Poland's Olympic Committee and relatives of those killed in the World War II Katyn massacre. Kaczynski and his party were to attend a memorial ceremony for the 20,000 Polish slain by Stalin's forces in 1940.
When the 26-year-old Tupolev Tu-154 airliner tried to land in Smolensk despite thick fog, it crashed and burned, killing everyone on board.
Russian Prime Minister Vladimir Putin heads an investigation into the crash. Initial reports suggest a pilot error.
New presidential elections are expected in May or June.