British bank Barclays confirmed on Friday that it had agreed to sell its BGI investment arm to U.S. firm BlackRock for $13.5 billion, creating the world's biggest asset manager.

Barclays said in a statement that a net gain of $8.8 billion would be used to bolster its capital strength, boosting the bank's equity tier 1 ratio by 163 basis points and its core tier 1 capital ratio by 150 basis points.

Including the impact from the conversion of convertible notes issued in November 2008, Barclays said its equity tier 1 ratio would have been 8.3 percent at the end of last year while its core tier 1 ratio would have been 8 percent.

In terms of current trading Barclays said its performance up to the end of May had been generally consistent with trends reported at the time of its interim statement on May 7.

(Reporting by Paul Hoskins, editing by Steve Slater)