Campaigners supporting the alternative vote have denied accusations that they "airbrushed" the black poet Benjamin Zephaniah out of leaflets distributed in the Home Counties, Hampshire and Cornwall.
The campaign used Zephaniah's picture as an endorsement on literature in London, but in other parts of the UK the leaflets featured the actor and broadcaster Tony Robinson, prompting accusations from rivals that the Yes campaign was "ashamed" of the poet's backing.
Yes-to-AV said it varied the celebrity backers featured on its leaflets as there were "a number" to accommodate.
"Let's put it this way: Operation Black Vote, the Muslim Council of Britain and a host of similar groups are backing the Yes campaign," a spokesman said. "The BNP are backing the No campaign. People can draw their own conclusions."
Meanwhile in a separate row over the voting reform referendum, which takes place on 5 May, the Liberal Democrat minister Chris Huhne accused the Conservative Party's chairwoman, Baroness Warsi, of using "secret donations to advance scares and smears" against advocates of the AV system.
He demanded that she reveal the source of her campaign's funding, adding: "Please stop now before you poison our politics."