The Lansdowne Park Conservancy says it will formally submit an unsolicited proposal for the development of the park next week.

The group says in a release there's over half a billion dollars difference between the private bid from the Ottawa Sports and Entertainment Group, which they say will cost taxpayers $300 million, and their non-profit proposal which they say would net the City $200 million as well as $55 million in tax revenue.

The LPC says under City of Ottawa procurement rules, a firm submitting an unsolicited bid that offers better value for the taxpayer will prevail, barring a counter-offer from the original group.

They said they would also be eligible for low-interest provincial infrastructure loans.

It was also announced the LPC is bringing in architecture company NBBJ, which has built stadiums for the Philadelphia Eagles, Cincinnati Bengals, Seattle Mariners, Milwaukee Brewers and Columbus Blue Jackets.

The LPC says under the terms of the Canadian Football League contract, a team would rent space from any City-owned stadium.

It would also be ready in 2014 for football, the Ottawa 67s and the 2014 FIFA Under-20 Women's World Cup, according to the news release.

This news comes after Friends of Lansdowne, another group opposed to sole-sourcing its development, announced Wednesday it is appealing the Superior Court decision to dismiss its case.