Gerry Adams challenged Secretary of State James Brokenshire on his silence over offensive material on Eleventh Night bonfires at a meeting in the US earlier this week.
The Sinn Féin leader held face-to-face talks with the Tory MP on Monday when both were in Washington DC on separate business.
Mr Adams, who was in the US capital for a Memorial Mass for Martin McGuinness, said he requested the meeting after learning through the media that Mr Brokenshire was visiting America this week.
Sinn Féin issued a statement about the meeting on Tuesday but the Northern Ireland Office (NIO) did not publicise the discussions.
The NIO declined to explain to The Irish News why the meeting took place Stateside and why it had not been publicised.
Asked if there was any comment on the meeting, an NIO statement said the opportunity arose in Washington to meet Mr Adams and discuss a number of issues.
"The meeting is in keeping with the secretary of state's approach, outlined at the conclusion of the talks in July, to continue to talk to all the parties with a view to restoring devolution as soon as possible," the statement said.
Speaking to The Irish News yesterday from Washington, Mr Adams said he raised concerns with the secretary of state about the British government's handling of legacy issues.
"I challenged him on his government's cover-up and refusal to give information to victims of British actions or the actions of their allies, as well as the quite deliberate withholding of the funding the lord chief justice has asked for to allow inquests to proceed," he said.
The Sinn Féin leader said Troubles' inquests was not solely a "republican position" but affected all victims of the conflict.
"I'm disappointed that it appears he is seeking to make this a negotiating position as we have refused to negotiate on it," he said.
"The right to an inquest is a very modest entitlement and should not be subjected to political negotiations – once again, this is one rule for people in the north and a different for those elsewhere in the British state."
Mr Adams said he challenged Mr Brokenshire on being "silent" about effigies and other offensive material appearing on a number of Eleventh Night bonfires, including a coffin bearing an image of Martin McGuinness.
"I asked him why he was silent on the antics around some of the bonfires around the Twelfth, because I'm sure he was as perplexed and outraged as anybody at the image of Martin McGuinness's coffin being burnt on a bonfire," he said.
The Louth TD said he did not get a "satisfactory answer to that question" from the secretary of state.
"It was obvious that like some unionist leaders, they prefer to be silent on these issues as opposed to making it very clear that this is unacceptable behaviour," he said .
"I put it to him that I couldn't imagine that in any part of London groups of disadvantaged or alienated young men could build a bonfire towering three-or-four storeys high on a public thoroughfare."
However, Mr Adams rejected suggestions that Mr Brokenshire's reticence was due to the Tories' recent pact with the DUP.
He said it was "par for the course" .
"I wanted to put it to him that this activity of a tiny minority would only be stopped if it became unacceptable in the public narrative and made illegal," he said.
Mr Adams told the secretary of state that Sinn Féin was "ready and able" to assume its place in the executive but only the basis which his party has previously outlined – "That is on agreements broken or not implemented being dealt with in an acceptable way."
