He added that the current constitution has many imperfections that need to be addressed.
Duda was speaking during a debate organised by his aides together with the Solidarity trade union in the northern port city of Gdańsk.
The debate, headlined "A Constitution for Citizens, not for the Elites?," was held at a historic hall in the Gdansk shipyard where striking workers in August 1980 signed a landmark agreement with the country’s communist authorities of the time.
According to the president, the most serious flaw of Poland’s current constitution, which dates from 1997, is that it imprecisely distributes powers among different authorities in the state.
While the current constitution has many legitimate solutions, Duda said, many of them do not work in practice and remain on paper.
One example, he said, is that the constitution defines Poland as a social market economy, a system that he argued does not yet exist in practice because it is still being built.
"There are many such areas ... where more precision is needed," Duda said.
The Gdańsk event opened a series of debates ahead of a referendum that the president wants to see taking place next year for the people to decide whether to introduce changes to the nation’s constitution.
When proposing the referendum, Duda said in early May: “Poles have a right to say whether the constitution, which has been in force for 20 years, should be changed.”
He added that Poles themselves should be able to decide on the directions of the country's development.
Duda has suggested 11 November 2018 as the date for a referendum on changes to the country's constitution.
Half of Poles are in favour of a referendum on potential changes to the country’s constitution, a poll found in June.
The survey by pollster CBOS also found that 47 percent of respondents were opposed to changes in the constitution, while 37 percent said they supported such a move. (str)