The FTSE 100 was down 0.5 percent and the FTSE 250 was down 0.3 percent by 0936 GMT.
HSBC was by far the biggest drag on the main bourse and on track for its worst day in almost two years, as recent uncertainty around the Sino-US trade situation was reflected in the Asia-focused bank's disappointing profit growth.
Its shares slipped 4.2 percent and the bank warned that weaker economic outlooks for China and Britain would pose more challenges this year, prompting Markets.com analyst Neil Wilson
to note that HSBC's focus on China and Asia was a "double-edged sword".
Spreadex analyst Connor Campbell said HSBC finds itself "stuck in the middle of a Venn diagram covering China's slowing economy, the concerns surrounding global trade, and Britain's Brexit mess."
The downbeat results knocked more than 20 points off the FTSE 100 and dragged peer Standard Chartered down 3.6 percent.
BHP Group fell 1.3 percent after first-half underlying profit at the world's biggest miner fell 8 percent as copper earnings slumped.
But InterContinental Hotels rose 1.4 percent as strong demand in China helped full-year room revenue grow.
High street baker Greggs jumped nearly 10 percent to an all-time high on the mid-cap index as sales rose in the first seven weeks of 2019 and it forecast higher full-year underlying pretax profit.
Japanese car maker Honda's confirmation of its decision to shut its only British car plant did not appear to have affected the wider market and the company said the move was not related to Britain's impending exit from the European Union.
The country's labour market also seemed to be staying buoyant ahead of Brexit, as official figures showed workers' pay growth held at its fastest pace in a decade in late 2018, and job creation remained strong.
A new round of China-US trade negotiations is expected this week and reports of progress in the talks, despite a lack of clear details, have raised hopes that the countries can reach a compromise by a March 1 deadline.
Online trading platform Plus500, which has slumped since last week after a profit warning and a drafting error in its 2017, report, fell for a seventh straight session. The stock was down 10 percent.
Bank of Georgia slipped 4.3 percent after warning that growth of unsecured consumer loans would moderate on the back of some newer rules, which took the shine off a jump in annual profit.