The racism in Othello is not as pronounced as the antisemitism in the Merchant of Venice, the director of the National theatre said this week.

Sir Nicholas Hytner, whose critically acclaimed production of Othello starring Adrian Lester and Rory Kinnear is currently selling-out at the National, expressed his view in conversation with JC theatre critic John Nathan at the London Jewish Cultural Centre on Monday evening.

Discussing how the interpretation and reaction to William Shakespeare's work has changed over time, he noted that in 1604, London audiences would have had a very different response to a man with black skin than they did in 1804 or 1904.

"It was written before we had learnt to be as racist as we became," he said. "I give you as evidence of this the Merchant of Venice. Same city, same world, there isn't a page in Merchant of Venice which isn't obsessed with Shylock's Jewishness."

Sir Nicholas, who is only the second person to have run the National Theatre for more than a decade, described Merchant as "an antisemitic play which contains within it a criticism of antisemitism".

"Everybody in the play is antisemitic, they ascribe everything bad that is done to Shylock's Jewishness," he said. "You can't imagine Shylock being appointed commander of the armed forces.

"In Othello it's not a big deal to the Venetian duke and the senators of Venice that they are appointing a Moor. Not many people in Othello are vocally racist."

Sir Nicholas, who announced earlier this year that he was standing down from the National in March 2015, said he hoped his swansong would be a production of a new play by an up and coming writer. Although he gave no indication of who his preferred successor would be, he said it was great "for a theatre to have an artist as chief executive".

His tenure at the National has seen collaborations with Habima, the Israeli theatre company that faced boycott calls when it performed at the Globe Theatre last year. "I don't personally agree with boycotts," he said. "None of my colleagues said let's not work with them."

But he also revealed that as a young pupil of Manchester Grammar School, he initiated his own boycott – of the school's Jewish choir, joining the non-religious one instead. "The standards were not high enough in the Jewish choir so I boycotted it on musical grounds."