Recent coverage of the war has increased tension in the media
The BBC World Service is to stop providing radio news to Sri Lanka's state broadcaster because of what it calls "deliberate interference".
A statement said FM broadcasts to the Sri Lankan Broadcasting Corporation would be suspended from Tuesday.
The BBC said many of its news reports in Sinhala, Tamil and English had been blocked or only partially broadcast.
The SLBC chairman admitted censoring BBC programming, saying he had a duty to do so at a time of war.
The BBC says it will maintain its services in Sinhala, Tamil and English on short wave radio and online. BBC news reports in English are to continue on the Sri Lankan commercial radio broadcaster, MBC.
The BBC move follows allegations that press freedoms are being eroded in Sri Lanka as fighting intensifies between troops and Tamil Tiger rebels.
Media rights groups accuse the Sri Lankan authorities of cracking down on dissent. The government denies the charge.
'Fabricated news items'
The BBC said it had expressed its concern directly to SLBC Chairman Hudson Samarasinghe in a series of letters and meetings in December and January.
"The BBC noted 17 instances of interference to BBC Tamil and eight similar instances to BBC Sinhala broadcasts between November 27 and early January. Sometimes whole current affairs segments of BBC programming were not broadcast on SLBC," the statement said.
"The BBC made it clear to SLBC that such interference and blocking meant that BBC programming was being editorially compromised by SLBC's actions and this was contrary to the BBC's contractual agreement with SLBC.
"Despite the warnings, last week there were several further instances of interference to BBC programming in all three languages being broadcast on SLBC."
BBC World Service director Nigel Chapman expressed dismay, but said he was prepared to have further discussions to resolve the issue.
Prabhakaran's voice should not be heard in Sri Lanka, the SLBC says
He promised to "investigate any specific detailed complaint SLBC may have about BBC output".
"So far, no specific complaint has been raised," he said.
Mr Samarasinghe told the BBC News website that Sri Lanka faced "terrorist attacks" and the media had a role to try to "restore peace and harmony".
"Some foreign news centres created fabricated news items about Sri Lanka," he said.
Asked if that included the BBC, he said: "Definitely."
He said the SLBC was not allowed to broadcast the voice of rebel leader Velupillai Prabhakaran - something the BBC had tried to do on rebel "heroes day" on 27 November.
"The SLBC is the national broadcasting corporation, the voice of Sri Lanka. When they broadcast Prabhakaran's voice - at that time I cut off the programme."