The blue-chip index slid 1.8%, with NatWest tumbling 3.3% after the UK government completed the sale of 1.1 billion pounds ($1.55 billion) in its shares at a discounted price.
All the FTSE 100 constituents were trading in negative territory.
Banks, travel and leisure, and miners were among the biggest losers, all down more than 2% each.
Globally, tech stocks took a brunt of the selling as investors braced for U.S. inflation data due on Wednesday while keeping a close eye on a host of Federal Reserve speakers this week to assess how authorities are likely to respond to receding risks posed by the pandemic in some major economies. [MKTS/GLOB]
The domestically focused mid-cap FTSE 250 index tripped 1.6%. Both the indexes were tracking their worst daily performance in three weeks. Reporting by Devik Jain in Bengaluru; Editing by Subhranshu Sahu