In a statement, Assura confirmed it had 'entered into exclusive discussions with another party regarding the sale of a majority interest' in its GPCo business.
Its GPCo business generated £7.6 million for the nine months to 31 December 2009, with nearly half of this amount earned in the past three months of 2009, the statement from Assura said.
The firm refused to comment on speculation that it was negotiating with the Virgin Group.
In September 2008, Virgin Healthcare abandoned its plans to take over an NHS practice in Swindon, and scaled back its plans for a chain of Virgin-branded health centres.
But when it pulled back from taking over the Swindon practice, Virgin Healthcare said it remained committed to general practice, and was in discussion with more than 300 practices.
Earlier that year, it had said it would not bid for APMS contracts, but would aim to work with existing practices, keeping existing GPs as the contract holders, but operating out of Virgin-branded health centres.
In an interim report released in September last year, Assura said it owned 30 GPCos, which covered a population of 3.1 million patients.
The firm's primary care contracts include a number of Darzi centres.