GLG Partners is being sued by an investor in the US who argues his shareholding in the group is undervalued in the proposed $1.6bn takeover by Man Group.
Man Group has agreed a deal to acquire GLG Partners for $1.6bn.
Broker downgrades and companies going ex-dividend pulled the FTSE index 25 points, or 0.4% lower this morning.
The FTSE 100 index fell by 0.4% on Friday, the first time it declined in four days. The benchmark index ended the day at 5703.02 points, off by 24.63 points.
The FTSE was up 27.5 points (0.5%) to 5271.63 points, buoyed by gains among mining firms.
Axa Ethical Distribution fund manager Richard Marwood has added to financial stocks this month and offloaded almost all traditional gilts on concerns of inflation.