Worsening relations between RTÉ and TV3 have been further soured by revelations the state broadcaster tried to prevent TV3 airing a documentary on the murder of Lord Louis Mountbatten earlier this month.

RTÉ's legal department contacted TV3 at 5.30pm on Monday 10 August in an attempt to stop the commercial broadcaster airing The Day Mountbatten Died.

RTE sources say the airing of the production, a BBC special revoiced for TV3, was intended as a "spoiler" for a new RTÉ special on Mountbatten, which had been heavily promoted by the station and was due to air on RTÉ a week later on 17 August.

The state broadcaster is said to have contacted TV3 to have the BBC special pulled because it featured RTÉ footage which they claimed had not been cleared by the station. RTÉ were also said to be angry the programme had not featured in advanced listings on TV3.

Ben Frow, TV3's director of programming, while conceding the transmission of the The Day Mountbatten Died "was a spoiler", said TV3 had been entitled to air the programme.

He said: "Was it a spoiler? You could call it a spoiler. We acquired it from the BBC and they [RTÉ] were very pissed off we showed it. They tried to stop us showing it.

"We got a phone call the evening it went out saying we couldn't show it because it had one minute 10 seconds of RTÉ footage. We acquired it from the BBC. We showed it. Their argument should have been with the BBC who we acquired it from."

TV3 have alleged RTÉ staged a similar spoiler the month before by deciding at short notice to broadcast live coverage of the funeral of Michael Jackson in competition with TV3, who had been advertising similar coverage up to a week before.

"They [RTÉ] succeeded very well. They wanted our audience and they got our audience. They cleaned up. On the day of Michael Jackson's funeral they decided to show the funeral without adverts.

"We had been trailing it for a week. Originally it was only Sky TV and TV3 who had been showing the funeral.

"RTÉ showed exactly the same thing as we were showing. They also dropped the adverts that night. Strange for a station which is meant to be strapped for cash. It shocked me," said Frow.

RTÉ declined to comment to the Sunday Tribune this weekend, either on attempts made to stop TV3 airing The Day Mountbatten Died or their decision to broadcast the funeral of Michael Jackson at short notice in competition with TV3.

An RTÉ station spokeswoman said: "As our most important stakeholder, the viewing public is our primary focus, and their expectations of the highest quality, diversity and range of home-produced programming, as well as the best and most timely international productions, is the key determinant of our scheduling of RTÉ One and RTÉ Two.

"This focus secures a competitive positioning of RTÉ vis-a-vis TV3, and all other television channels."