Nisa members could receive more than £2,000 per share, Co-op-branded products and the chance to sign up to a franchise if they give the Co-op approval to buy Nisa.

Documents seen by Retail Express reveal that the multiple retailer has put together a £144m deal for Nisa retailers – beating Sainsbury’s previous offer said to be £130m.

The offer includes £460 paid upfront for every share, with a further pot of £1,700 paid out over three years.

A franchise model will be made available to shops that meet certain criteria, and Co-op-branded lines will be rolled out to selected stores.

The deal also promises that the group will attempt to improve Nisa’s buying prices and will retain mutuality for members.

A retailer who did not want to be named told Retail Express they would vote for a sale: “Nisa is not in a good place. The company has been dragged down in the past few years and a lot of core benefits such as pricing, promotions and availability have been lost. It could be that the Co-op can give us what we need.

They added: “If Nisa don’t agree a sale, and Booker and Tesco get the go ahead, Nisa will get left behind.”

A spokesman for the Co-op  said: “We can confirm that we’ve entered into a period of exclusivity with Nisa, which will provide the opportunity for us to carry out more detailed due diligence in the coming weeks.

“Following this period and subject to approval from our Board, we hope to be in position where we can put forward an offer to Nisa members.”