There has been criticism over how a letter from Prime Minister Theresa May to Northern Ireland’s political leaders was unveiled.
First Minister Arlene Foster and deputy First Minister Martin McGuinness sent a message to the PM in August asking about the impact of Brexit and received a response dated 14 October.
The details emerged on the radio on Tuesday morning.
Raising the matter at Stormont, the UUP MLA Stephen Aiken asked “whether it is appropriate for important documents that will have influence on debates in this Chamber to be released to the Assembly first, rather than to The Stephen Nolan Show this morning”.
Speaker Robin Newton responded: “It will be my practice to continue to ask ministers to come to the House when they have something to report.”
Alliance MLA Stephen Farry said it was disappointing that the letter had not been revealed ahead of the Brexit-related Assembly debate on Monday.
He added: “Once again, it is disappointing we are hearing developments relative to Brexit in the media first, instead of the chamber.
“There is a major accountability deficit from the First Minister and deputy First Minister, who have yet to even mention the Prime Minister’s response to the Assembly.”
Arlene Foster has denied there was any attempt to keep the letter a secret.