The DUP revealed the initial email inviting Mr Corbyn which Labour had not responded to for 10 days.
Labour yesterday said Mr Corbyn didn't receive the invitation until Wednesday. It apologised to the DUP for the delay which it insisted was unintentional. It said it would investigate how it happened.
Mr Corbyn strongly denied he was snubbing victims. In an interview with the Belfast Telegraph yesterday, he said he would not be meeting them during this trip as his schedule was very tight.
But he added that shadow Secretary of State Tony Lloyd was available to do so.
"Tony is very happy to meet the families of victims and we will do so. I have no plans to meet them during this visit," the Labour leader said.
When asked if he personally was willing to meet IRA victims in future, he said: "I have no problem about meeting anybody.
"Tony will meet them first and we'll take it from there."
Mr Corbyn said he was available to hold discussions with all Northern Ireland's main political parties, including the DUP, during his visit.
DUP MP Gregory Campbell first sent correspondence to Mr Corbyn's Westminster email address on May 14. He said he believed it would be helpful for the Opposition leader to meet victims who lived near the border.
Mr Campbell said he also hand-delivered the invitation to a Labour MP to pass onto Mr Corbyn earlier this week.
The party said this was not passed onto Mr Corbyn's office.
In correspondence to Mr Campbell yesterday, a Labour official said: "I would like to apologise for the process failure that resulted in your original email to Mr Corbyn not being responded to. I will investigate as to how this occurred and I can assure you that a lack of response was unintentional."
Unionists remained critical of the Labour leader. DUP MP Sammy Wilson said: "Jeremy Corbyn's visit confirms what many people already thought about him. His support for the break-up of the United Kingdom and refusal to engage with victims of republican terrorism come as little surprise.
"Neither would his desire to keep Northern Ireland entrapped within the European Union."
Mr Wilson said that the Labour leader had an opportunity to distance himself from republicans. "However, he has not even tried to avail himself of the opportunity and in doing so proven himself unworthy of a vote anywhere in the United Kingdom," the DUP MP said. UUP leader Robin Swann said Mr Corbyn's visit provided him with an opportunity to condemn the IRA. "Whilst Jeremy Corbyn is here in Northern Ireland, I hope that he will finally state unequivocally that the IRA's campaign of murder was completely wrong and totally unwarranted," Mr Swann said.
"I would especially invite him to acknowledge the fact that people like Ulster Unionist Assembly Member Edgar Graham - murdered by the IRA on the Queen's University campus in 1983 - did not need to die in pursuit of their goal of a United Ireland."
The UUP leader said the murder of an elected representative should be "a reminder to Mr Corbyn of the fascist nature of the IRA and its campaign".
He continued: "As the current leader of the Labour Party, Mr Corbyn's words and deeds carry more weight than when he was a backbench MP. Today provides him with an opportunity to state clearly where he stands on terrorism and violence used to try to achieve a political goal." Kenny Donaldson of Innocent Victims United (IVU) said it had so far been unsuccessful in arranging a meeting with Mr Corbyn despite repeated attempts.
"IVU has requested on countless occasions that Jeremy Corbyn would meet with the innocent victims of PIRA terrorism and we have done so through directly contacting his office and also via issuing the request publicly through the public press," Mr Donaldson said.
"For several years he has stonewalled those requests and even now when actually here in Northern Ireland, neither he nor his party have any interest in dealing with these issues.
"That is not the action of someone who would have ambitions to be Prime Minister, it is the actions of someone who does not possess true leadership qualities nor an ability to front up on difficult issues."
Dear Mr Campbell,
Thank you for taking the time to speak to me earlier.
I would like to apologise for the process failure that resulted in your original email to Mr Corbyn not being responded to, I will investigate as to how this occurred and I can assure you that a lack of response was unintentional.
We were made aware by the media that a letter would be hand delivered to our office, and after speaking to you it transpires that this was given to via the Whips Office, however, this was not received in our office.