Donald Trump’s son-in-law Jared Kushner has been granted White House security clearance after a lengthy background check.

The move ensures the key adviser with a broad international portfolio can have access to some of the US’s most closely held secrets.

Mr Kushner, a senior adviser on the Middle East and other issues, was among many White House advisers who had been operating without approval for full security clearances.

That led to a White House policy overhaul in February that significantly downgraded access to sensitive information for Mr Kushner and other Trump administration officials on interim clearances.

Jared Kushner with his wife, Donald Trump’s daughter Ivanka
Jared Kushner with his wife, Donald Trump’s daughter Ivanka (Sebastian Scheiner/AP)

“With respect to the news about his permanent security clearance, as we stated before, his application was properly submitted, reviewed by career officials, and went through the normal process,” Mr Kushner’s lawyer Abbe Lowell said in a statement.

“Having completed these processes, Mr Kushner is looking forward to continuing the work the president has asked him to do.”

Mr Kushner was interviewed for a second time last month by the office of special counsel Robert Mueller, who is investigating potential ties between the Trump campaign and Russia.

“In each occasion, he answered all questions asked and did whatever he could to expedite the conclusion of all the investigation,” Mr Lowell said.

The first interview occurred last autumn and the questions were limited to former White House national security adviser Michael Flynn, who subsequently pleaded guilty to lying to the FBI and began co-operating with Mr Mueller.

The second interview was in April and concerned potential influence by foreign governments, including Russia, and the firing of former FBI director James Comey, among other topics, Mr Lowell said.

The interview did not deal with Mr Kushner’s finances or his companies, Mr Lowell said.

Mr Kushner was with the president in New Jersey the weekend before Mr Comey was fired, 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 receive negative information about Hillary Clinton.

Mr Kushner — the point of contact for foreign officials during the campaign and transition — was also alluded to, though not by name, in Mr Flynn’s guilty plea as a transition team official who encouraged Mr Flynn to contact foreign government officials, about a UN Security Council resolution against Israeli settlements.

The delay in Mr Kushner’s case was caused by a backlog in the new administration and his extensive financial wealth, which required lengthy review, Mr Lowell said.