Convenience chains Costcutter and Nisa Today’s are embroiled in a row after Costcutter chairman Colin Graves resigned from Nisa Today’s board in a dispute over a conflict of interest.

Graves said he was leaving the board because he had been excluded from some board discussions.

Nisa Today’s chief executive Neil Turton said he was “very disappointed” Graves chose to make his announcement at a Costcutter conference in Barcelona.

Costcutter is 51% owned by Bibby, a family conglomerate that tried to buy Nisa-Today’s last year.

Turton said lawyers had advised the Nisa Today’s board to exclude Graves from certain discussions on distribution contracts, as Bibby could tender for them.

Nisa-Today’s has a contract to supply Costcutter until 2014 but it is terminating a £70m annual distribution deal with Bibby next year, according to the Financial Times.

Costcutter managing director Nick Ivel said that decision “sparked a conflict” and since then, Nisa-Today’s had been trying to poach its members, which Turton rejected.