Byrne currently reports to Observer news editor Andy Malone. Byrne and Malone run The Observer newsdesk and the Focus section along with the Sunday broadsheet's deputy editor, Paul Webster.
Malone said Byrne had been instrumental in developing Focus's news analysis pieces. 'He has enabled us to get a hold of the Focus pages, bolstering the number of ideas in the newsroom,' Malone added. Byrne also worked on The Observer's Irish edition.
Byrne will report to Martin Clarke, editor in-chief of Associated Newspapers in Ireland. Associated bought Ireland on Sunday from Scottish Radio Holdings last September.
Before joining The Observer in his current position 18 months ago, Byrne was foreign editor of Edinburgh-based Scotland on Sunday. He was previously a reporter on The Sunday Telegraph and a trainee at The Sunday Times.
Byrne resigned last week and no date for his departure has been set.
'At the moment, the plan is to find a direct replacement,' Malone said.