SDLP MP Alasdair McDonnell has said he is personally saddened by Michael Martin's decision to resign as Speaker of the House of Commons.
The South Belfast MP said though the Speaker's position had become untenable he felt he had been made a scapegoat.
Sinn Fein MP Conor Murphy said the resignation was not the answer to the expenses controversy.
He said the public wanted a system in place that showed that money is spent in a transparent way.
Mr Martin told MPs on Tuesday afternoon that he intended to stand down as Commons Speaker, amid criticism of his role in the MPs' expenses row.
He told MPs he would relinquish the office of Speaker on 21 June - to maintain "unity" in the House.
In a short statement to a packed House of Commons he said a new Speaker would be elected the following day.
A motion of no confidence in him has been backed by 23 MPs. Mr Martin is also expected to step down as an MP.
It is the first time a Speaker has been effectively forced out since 1695.