June 23 (Reuters) - Britain’s GSK on Wednesday unveiled a detailed plan to spin off its consumer healthcare venture with Pfizer into a separate company by the middle of next year, as the pharmaceutical giant sharpens its focus on prescription medicines and vaccines. The separation will be achieved by demerging at least 80% of GSK’s current 68% shareholding in the Consumer Healthcare business to GSK shareholders, with the shares in the new entity to list on the London Stock Exchange. Reporting by Pushkala Aripaka in Bengaluru and Ludwig Burger in Frankfurt; editing by Jason Neely Our Standards: The Thomson Reuters Trust Principles.