(Reuters) - Marshall Wace is planning to raise $1 billion for a new fund which will invest based on environmental and other ethical criteria, a source familiar with the matter told Reuters. The hedge fund, co-founded by British financier Paul Marshall, will rely on external analysts who focus on environmental, social and governance (ESG) issues, the source said on Saturday. The fund will bet against stocks with poor ratings and will buy stocks with strong ESG characteristics, the source added, confirming an earlier Financial Times report.