It comes as it was revealed that Kieran Hartley, the substitute for Mr Crowley, complained three times to Fianna Fáil leader, Micheál Martin, over the the fact that the MEP has not attended any European Parliament meetings since his election in 2014.
Mr Crowley has been in hospital for some time and has been unable to attend parliament sittings.
However, MEPs cannot be replaced until they make a personal decision to resign. At that stage, their substitute takes up the seat.
Mr Crowley, like all other MEPs, is still entitled to receive the MEP basic salary of €8,484,05 a month as well as a €4,342 monthly general expenditure allowance to cover office rent, telephone and postal charges and other constituency activities.
MEPs are also entitled to a reimbursement of two-thirds of their medical expenses.
Co Kerry Fianna Fáil TD, John Brassil yesterday, criticised Mr Hartley after it emerged that he has written to the party leader on three occasions.
In correspondence, Mr Hartley said Mr Crowley’s absence means Fianna Fáil is not represented and this put the party in a difficult position given the negotiations ahead with Brexit.
Reacting Mr Brassil said: “To me, Brian making a full recovery is the most important thing.”
He said that approaching Fianna Fáil headquarters to make a complaint is “insensitive” and “inappropriate”.
Another Fianna Fáil TD last night said that it may have been a case of Mr Hartley being “overeager” to take up the position.
“I think maybe he has gone about it the wrong way and it might not help him in the long run.”
Mr Crowley, who has been paralysed from the waist down since he was a teenager, was elected an MEP for Ireland South in 2014, but has been absent from parliament ever since.
A spokesman for Mr Crowley said: “Brian is in the Cork Regional Hospital recovering from a series of leg and hip operations and, once discharged, will personally address all and every issue.
“However, he has still been working away from his hospital base and through his office staff,” the statement read.
However, he declined to say whether Mr Crowley’s office in Brussels is still being staffed and said he will not be answering anything outside of the statement.
There was no response when efforts were made to phone his offices in Brussels and Strasbourg yesterday.
His substitute, Mr Hartley, pointed out that, as it stands, Fianna Fáil has no representation for 1.4m people in the Ireland south constituency at the same time as Brexit is taking place.
“On a political level, we need representation in the European Parliament,” Mr Hartley told RTÉ’s Séan O’Rourke.
A Fianna Fáil spokesperson said: “Brian was elected to the European Parliament in 2014 with the single largest vote in Ireland and while he is currently suffering from ill health, we understand that his office continues to provide a full range of services to constituents.
“We wish Brian a full and speedy recovery.”