Pressured by a firm sterling , the export-oriented FTSE 100 (.FTSE) was down 0.5% at 0710 GMT.
The FTSE 250 (.FTMC) mid-cap index shed 0.7%.
After data showed consumer inflation was unchanged at 8.7% in May, contrary to expectations of a slight fall, traders ramped up their bets of a 50 basis point (bps) BoE rate hike on Thursday from the 25 bps hike anticipated earlier.
In a testimony later in the day, Powell is poised to be questioned on the future of rate hikes by the world's most influential central bank.
Reporting by Ankika Biswas in Bengaluru; Editing by Sonia CheemaOur Standards: The Thomson Reuters Trust Principles.
Persons:
Jerome Powell, BoE, Powell, homebuilder, Ankika Biswas, Sonia Cheema
Organizations:
Bank of England, Federal, FTSE, Berkeley Group Holdings, Thomson
Locations:
Bengaluru