The Oireachtas members’ bar and the visitors’ bar have both been closed for the day after a large rat was seen on the premises.

The rat was spotted by Fianna Fáil leader Micheál Martin, who was in the Dáil bar on Tuesday. Mr Martin is said to have seen the rat along the floor while having a cup of tea with Fianna Fáil Roscommon TD Eugene Murphy, and then informed staff of the discovery of what was described by well-placed sources as a “big, fat fella”.

It has since emerged that later in the evening, a rat - presumed by staff in Leinster House to be same the rat - appeared from underneath a couch in the visitor’s bar and scurried across the floor.

Fianna Fáil justice spokesman Jim O’Callaghan was sitting on the couch with guests at the time. The rat ran over the foot of a friend Mr O’Callaghan had invited into Leinster House for dinner.

Staff, armed with a golf club that is kept behind the bar, gave chase to the rat but it escaped once more.

The physical separation between the members’ bar and visitors’ bar in Leinster House is akin to the split between a bar and a lounge in a normal pub, although only TDs and senators are allowed enter the members’ bar.

It was assumed the rat entered the bar through a hole in the floor but, despite an extensive search, was not found.

The Leinster House rat remained at large on Wednesday and both bars remain closed as staff try to locate the rodent.

An Oireachtas spokeswoman said: “Leinster House is an an old Georgian building, so these things happen.

“Refurbishment and building works are being carried out, so it is not surprising that a rat would get into the building as there are plenty of old drains it could have come out of.”

On Wednesday the spokeswoman confirmed that the health inspectors had been called in to examine Dáil catering facilities as a precautionary measure, but that the inspectors were satisfied that all the necessary steps were being taken.

The 274-year-old Kildare Street building, built in 1745 as the home of the Duke of Leinster, has been undergoing major refurbishments for more than a year.

A 2006 survey of the building found Leinster House was a fire trap and the floors were sagging, creating a fire hazard in the space between them and the ceilings.