Royal Mail has apologised for any distress caused after some of its stamps were combined with a photograph of the late founder and leader of the Tamil Tigers.
The Sri Lanka High Commission said a front organisation for the Tigers had been able to get a stamp released with a photograph of Velupillai Prabhakaran, who was killed in fighting with the Sri Lankan army in 2009.
Individuals can personalise their mail by combining one of its stamps with a photograph through its "Smilers" service to create photo-stamps.
A spokesman said the Royal Mail had "stringent checks" in place to ensure that offensive images were identified and declined and the offending stamps had been blocked.
"As soon as we became aware of concerns about a small number of Smilers, Royal Mail cancelled the account set up by an individual and stopped the order," they said.
"We apologise for any distress that may have been caused to anyone who may have received a letter bearing this Smiler."
Prabhakaran battled against the Sri Lankan government for more than 25 years, with the goal of creating an independent Tamil state. The European Union has classified the Liberation Tigers of Tamil Eelam (LTTE) as a terrorist group
Earlier this month the French government had to apologise to the Sri Lankan government after its post office issued similar stamps supporting calls for an an independent Tamil homeland.
The stamps that featured Prabhakaran's image were custom made using a similar service as offered by the Royal Mail in Britain.