Action is the jewel in 3i's portfolio and its largest investment. The buyout firm said it had decided to increase the book value of its Action investment to 1.46 billion pounds after a liquidity discount, up from 902 million pounds as of end March.

"3i is actively engaged in the further development of Action and is not intending to sell its investment or organise a flotation of Action in the near future," 3i said.

($1 = 0.7471 pounds)

(Reporting by Freya Berry; Editing by Elaine Hardcastle)