Powergen have decided to end their sponsorship association with both codes of rugby in order to concentrate all resources on football.
The Football Association announced a fortnight ago that E.ON, Powergen's parent company, will be the title sponsors of the FA Cup from next season.
As a result, the Rugby Football Union and the Rugby Football League are seeking new competitions sponsors.
Mike Thompson, Powergen's head of sponsorship, said: "The sponsorships have come to a natural conclusion for us as a business."
"With our recent announcement that E.ON, our parent company, is to become a lead partner with the Football Association from August 1, 2006 this will now become the focus of our sponsorship strategy moving forwards."
The RFU will be forced to rebrand the new-look Powergen Cup - which pitches the 12 Guiness Premiership clubs with the four Welsh regions - a year into its existence.
The new Powergen Cup was signed up for four years by the BBC and more than 40,000 tickets have been sold for the semi-final double-header on March 4 in Cardiff, where Leicester take on Wasps and Bath play Llanelli.
But the RFU are already looking at ways to restructure the competition to reduce conflicts between club and country in the season. The Welsh Rugby Union are set to deny Llanelli their international stars for the semi-final because the match falls a week before Wales play Italy in the Six Nations Championship.
Nevertheless, the RFU and Premier Rugby - the English clubs' umbrella body - view the competition's first season as a great success. RFU business operations director Paul Vaughan said: "It has been an excellent partnership for everyone involved and the new-look Powergen Cup, with its increased attendances, will be a lasting testament to their involvement. Our focus now is to find a new partner who will be as committed as Powergen so that we can continue to have exciting competitions across all levels."
The RFL, having had Powergen sponsor their Challenge Trophy since 2003, are confident of attracting new sponsors for the Cup, which is worth more than £1million a year. Powergen were heavily involved in community and youth rugby in both codes.
