LONDON, June 25 (Reuters) - Banks, investors and big drug companies should consider creating a 10-billion-pound ($15.7 billion) "megafund" to help biotech firms in London and across Britain compete with U.S. rivals, London mayor Boris Johnson said on Thursday.

Britain is a leader in academic scientific work and also home to two of the world's top drugmakers - GlaxoSmithKline and AstraZeneca - yet emerging life science companies often find it difficult to secure funding.

The suggested new pool of debt and equity finance is designed to help plug that gap and is one of a number of ideas being floated at a conference in London bringing together leading figures in industry, finance and research.

The meeting includes representatives from Eli Lilly, Pfizer, Imperial Innovations, Silicon Valley Bank, the European Investment Bank and JP Morgan.

"We hope to harness our role as a global financial centre that will bring more life-saving drugs to market and deliver a huge boost to the economy," Johnson said.

The suggested megafund would be able to invest in multiple drugs at different stages of development, with investors receiving a percentage of the royalties from successful products or licensing revenues that result.

($1 = 0.6376 pounds) (Reporting by Ben Hirschler; Editing by Pravin Char)