Senators received €240,000 in travel expenses during lockdown despite the Seanad being closed during April and May.
The 48 Senators were given payments for April and May even though the Seanad was shut.
Fianna Fáil Senator Malcolm Byrne, who waived his travel expenses for May, defended the payments.
He said the fact that the Seanad was not sitting "doesn't mean that Senators weren't working".
"I can certainly say that all of my colleagues at the time were working".
"Even though I didn't claim it, it wasn't a case that I wasn't travelling during the period in order to attend meetings and so on in Dublin.
"So I think it is fair to say that Senators would have been travelling during the period and would have been attending meetings.
"I think the other core point, that Senator Alice Mary Higgins makes, there is also a requirement on Senators to have attended a number of days - where like in anyone else's job you've to fob in and so on.
"At the end of the year, all of that will have to be reconciled."
Senators receive two types of allowances – one for travel and accommodation and one called public representation allowance.
Senator Byrne explained: "There are probably a number of things to look at here: first of all what are the expenses and so on that are paid?
"So there are two types of expenses that are paid to members of the Oireachtas: one is a kind of a representational allowance, which deals with the normal running of their office, for research, for advertising and services, and clinics and things like that.
"And the other is the travel and accommodation allowance, which is designed to cover where TDs and Senators are travelling to Dublin for the purposes of meetings in and around the Houses of the Oireachtas."
However, he did admit that "it's not good PR", but added: "You've got to remember that it is an expense, it's not money that kind of goes straight into Senators' pockets".