The leader of British group Portishead has attempted to shame singer/songwriter the Weeknd in their ongoing row over a sample by posting the producer's request letter on Twitter.com.

Glory Box hitmaker Geoff Barrow maintains the R&B star improperly used a sample of his group's 2008 single MAChine Gun on his 2013 single Belong to the World.

The Weeknd argued he did not use a sample and that the music in the song was not similar enough to MAChine Gun to warrant infringement.

But now Barrow has stepped up his claim by posting a letter from a representative for the Weeknd, dated February, 2013, in which a rights sample is requested.

Barrow writes, "I think it's a load of bollox (sic). When someone asks to sample you and you refuse, they should have the respect as a fellow artist to not use it.

"We usually give sample clearance to tunes we like. It's got f**k all to do with money...! I just want my beat back."

Posting the letter from the Weeknd's rep, Barrow adds, "Hey kids, part one of 'No infringement.'" He then posted the Weeknd's Twitter user name.