By Huw Jones LONDON (Reuters) – Britain’s six-year drive to increase the number of women in senior management at financial firms is “stagnating” for the first time, a review for the finance ministry said on Thursday. The ministry launched its voluntary Women in Finance Charter in 2016 and more than 400 firms have now signed up. A review by New Financial think tank found that 78% of signed-up firms are meeting or are on track to meet their targets, up 5% on last year. The average level of female representation in senior management remained flat at 33% in 2021 compared with 2020, the review said…