Casually dressed TDs are to be urged to smarten up by the Dail Committee on Procedure and Privileges
However, the Green Party said last night it would not be ordering its newly-elected TDs to don shirts and ties to conform with the stricter dress code.
The Irish Times has also learnt that TDs are to be discouraged from using written scripts when contributing to Dáil debates. The Ceann Comhairle is expected to make an announcement on the use of scripts on Tuesday, and the move will put many TDs on the spot next week with hours of debate over the Budget.
The ruling on a dress code and the use of scripts are contained in an updated memorandum on decorum agreed by the Committee on Procedures and Privileges on Wednesday.
According to committee sources, there has been concern in recent years at the increased use of scripts in Dáil debates.
Although they will not be banned outright, scripts will be "discouraged" but notes will be allowed.
The move was welcomed last night by newly-elected Fine Gael TD Mr John Deasy, who has expressed his concern at the overuse of scripts.
Mr Deasy yesterday asked the acting Ceann Comhairle for a ruling when Sinn Féin TD Mr Caoimhghín Ó Caoláin stood up to read from a prepared script.
Mr Deasy said Sinn Féin was the worst offender. "I bet you a lot of the time they wouldn't be able to answer questions on what they have read out," he said. If all the parties agreed to cut out scripts, it would lead to livelier and freer debate, and would speed up the passage of legislation, he said.
"Since I was elected a TD six months ago, only three Bills have passed through the house. That is far too slow," said Mr Deasy.
Meanwhile, Green Party TD Mr John Gormley said the party's three newly elected TDs, Mr Eamon Ryan, Mr Ciaran Cuffe and Mr Paul Gogarty would not be changing from open-neck shirts to ties in future.
The memorandum on decorum updates the dress code to ask that it "reflect the dignity of the House".
"What is far more important is Dáil accountability, not what you wear in the Dáil," he said.
"I think people are more relaxed nowadays and ought to be. Look at successful businessmen like Richard Branson and Michael O'Leary. They don't wear ties."