The Sinn Féin leader, Mr Gerry Adams, and former Northern Ireland Secretary and British Cabinet Minister, Mr Peter Mandelson, are expected to appear on TV3's Dunphy Show Live tonight amid falling ratings.
Meanwhile, Pat Kenny will be interviewing model Ms Rachel Hunter and British TV personality, the former pop star of the 1960s, Ms Cilla Black, on the Late Late Show on RTÉ 1, which has recorded an increase in audience figures.
Since its launch three weeks ago, Dunphy's show has attracted an average total audience of 260,000 compared to 615,000 for RTÉ's Late Late Show.
In the first week the show achieved a total audience of 342,000, but this fell to 157,000 last week.
Commissioning editor at TV3, Ms Jane Gogan, said the station never expected to beat the Late Late Show in the early stages.
"We regard the current figures as fluid. Both shows are only three weeks old this season. This is not a sprint, it is a marathon and we are growing the audience on TV3 on Friday nights," she said yesterday.
Ms Gogan rejected the suggestion the station was finding it hard to book international guests.
"Each show is different and has a different feel, we have several high-profile guests lined up whom we believe will interest our audience.
"We are happy with the age of the audience and the balance of men and women," Ms Gogan said.
She said the response from the public had been very healthy, with 1,800 mainly positive comments on the show's comment line last week.
Advertisers, however, were more circumspect. Ms Martina Stenson, managing director of Universal McCann said: "It is interesting to note that while Dunphy's confidence has grown since show one, the viewing figures have moved in the opposite direction.
"Week one saw 319,000 adults over 15 tune into Dunphy, in week two this fell by 18 per cent to 260,000 and week three saw another fall in viewing figures to 151,000 viewers, this represented a 53 per cent drop from week one."
She said it was always going to be difficult to go up against a show with the heritage of the Late Late Show.
Meanwhile, RTÉ has appointed Mr Noel Curran as managing director of RTÉ Television.
He replaces Mr Cathal Goan who is director general designate.
Mr Curran will take up the post with immediate effect. A native of Co Monaghan, he joined RTÉ in 1992, after a period working as a business journalist and deputy editor with Business and Finance.
During his time in RTÉ Mr Curran has worked as a reporter, producer and editor in RTÉ Television, most recently as the editor of current affairs in the news division.