Abbe Lowell, who has represented Kushner in the Russian Federation investigation, told CNN that questions asked of Kushner during the April interview were "the appropriate topics that Bob Mueller and his team were looking at".
Another attorney for Kushner, Jamie Gorelick, said that Kushner's security clearance form, known as an SF-86, was "prematurely submitted" and that "among other errors, [it] did not list any contacts with foreign government officials".
That move was the result of a decision by White House Chief of Staff John Kelly to withdraw the temporary top secret clearances from those employees who had held them for more than eight months without the required background investigations on them having been completed.
His lawyer, who said Kushner recently sat for a second interview with Mueller's team, denied that those mistakes had anything to do with the delay.
"A year ago, Jared was one of the first to voluntarily cooperate with any investigation into the 2016 campaign and related topics", Lowell said in a statement.More news: 40 feared drowned as boat capsizes in Godavari River in Andhra Pradesh
"He has continued this complete cooperation, providing a large number of documents and sitting for hours of interviews with congressional committees and providing numerous documents and sitting for two interviews with the Office of Special Counsel", Lowell said.
Kushner's lawyer said Wednesday that Kushner completed the background check process that began past year.
Kushner was with Trump in New Jersey the weekend before Comey was sacked, and he was among the attendees at a June 2016 meeting at Trump Tower with a Russian lawyer at which the president's oldest son was told he would negative information about Hillary Clinton.
Federal Bureau of Investigation background checks for security clearances routinely examine an applicant's financial holdings and foreign contacts.
It was not immediately clear whether Kushner had access to some classified material in the months since his clearance was downgraded.
Kushner attended a meeting in June 2016 with a Russian at Trump Tower during the campaign in an attempt to get disparaging information on Hillary Clinton, and he attempted to set up a "back channel" to the Kremlin during the presidential transition. But those were not the only issues delaying Kushner's clearance.