John Bache, the president of the Magistrates Association, claimed that a more representative set of magistrates would ensure that those accused of crimes feel less alienated from the legal system.
Convicted criminals may not become magistrates, but the guidelines of the Ministry of Justice warn serious offenders of applying.
M. Bache said: "We all make mistakes, we all do things that we should not have done.
"But we want to increase diversity, and if we say that someone who has ever done something wrong will never be appointed, then that is not at all to increase diversity."
He added, "I would not want candidates to think that because a few years ago they had a relatively small criminal record that they would not be accepted as magistrates, because that would be completely wrong.
"People do not apply from ethnic minorities because they feel that people from their background do not become magistrates and that is clearly incorrect."
There are only 16,000 magistrates in England and Wales, which is less than half of 20 years ago, said Mr Bache earlier.
Another 9000 magistrates are needed to increase the number, he said.
Only twelve percent of the magistrates have a black or minority background and only four percent are younger than 40, compared to 55 percent who are over 60 years old.
In the Daily Telegraph, Mr. Bache said, "We are trying very hard to increase diversity, but it is not as easy as you might think.
"To begin with, people do not ask from the same ethnic minorities as white people – because they feel that people with their background do not become magistrates, and that is clearly incorrect."
Last year, Labor MP David Lammy reported the lack of black and ethnic minority magistrates.
Lammy said, "If you see three white faces, as Lammy has pointed out, and you are from an ethnic minority, the perception may be that they are not on your side.
"That would be wrong, but you can understand that this is perhaps the perception."