A deal for the sale of forecourt retailer Murco is close to completion, The Grocer can reveal.

Property agent Christie & Co has been instructed to act on behalf of a party interested in acquiring the business, which was put up for sale in July by its US parent company Murphy Oil.

Christie & Co and Murco are both remaining tight-lipped on the sale, but it is believed that Costcutter, whose biggest customer is Murco, is in the frame for the 457-site business.

Costcutter, owned by Bibby Line Group, has stores on 90% of Murco's estate. Murco has worked with Costcutter since 1997 and in April last year extended its supply contract with Costcutter until June 2012. Bibby Line Group has also admitted it is looking for further acquisitions in retail following two thwarted bids for buying group Nisa-Today's last year.

A sale to another party could jeopardise this contract in the longer term, said a senior industry source. "It could affect Costcutter as it is quite a large proportion of its sales," he said. "The contract was recently tendered though and re-secured, so it has some security for the next couple of years."

Costcutter would not be drawn on its interest in Murco, but a spokeswoman said: "We have a great ­relationship with Murco. We have a strong partnership and it is business as usual."

Malthurst Group, which is part of MRH (GB), and Irish forecourt operator Applegreen have also been touted. Applegreen has 13 UK sites and in May last year said there was potential to grow this to as many as 60 by 2015. It would not comment on Murco.

Fuel operators Jet, Gulf and Harvest Energy could also show an interest.

Murco's estate, which includes 234 company-owned sites and 223 dealer sites, could also be broken up to aid the sale, added another industry source.

"The sites are very average and many need updating," he said. "If I was Murco, I would sell sites off individually rather than as a block as that would ­maximise the asset."