Blue chip shares fell in afternoon trading as investors focused on the protectionist side of US President Donald Trump's business agenda.
Markets reacted nervously to the president's order to ban people from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen from travelling to America.
The FTSE 100 Index fell 48.8 points to 7136, as firms as diverse as Starbucks to Google raised concerns about moving its staff around the globe. The FTSE 250 Index was down 68 points to 18122.8.
Most major European markets were also lower in early afternoon trading.
IG market analyst Joshua Mahony said indexes were "turning their focus away from Donald Trump's business friendly measures and towards his more controversial decision to ban citizens and refugees from seven states in the Middle East and Africa".
In London, one of the strongest risers in the top flight was mobile phone giant Vodafone, which said it is in talks with Indian conglomerate Aditya Birla Group about a merger between Vodafone India and Idea Cellular, creating India's largest telecoms company.
Vodafone confirmed recent media speculation following a tough price war in the Indian market, sending the group's shares up almost 3%.
India's three leading mobile operators, Bharti Airtel, Vodafone and Idea, have been under pressure since the arrival of Jio Infocomm, a new operator owned by the billionaire Mukesh Ambani which has shaken up the market by offering free voice and data to customers.
Vodafone's shares lifted 5.1p to 198.4p.
The biggest afternoon risers in the FTSE 100 Index were DCC (+285p to 6475p), Vodafone (+5.1p to 198.4p), Antofagasta (+11p to 833.5p), Kingfisher (+3.4p to 336p) and Convatec Group (+2.1p to 247p).
The biggest afternoon fallers in the FTSE 100 Index were Old Mutual (-8.1p to 205.1p), Tesco (-6.6p to 200p), Mediclinic International (-22p to 788.5p), Barclays (-4.6p to 226.1p) and Hikma Pharmaceuticals (-35p to 1820p).
The biggest afternoon risers in the FTSE 250 Index were Atkins (+89p to 1489p), Hill & Smith (+34p to 1169p), IP Group (+5.6p to198.3p), Zoopla Property Group (+9pto372.90p) and Pagegroup (+9.1p to 442.2p).
The biggest afternoon fallers in the FTSE 250 Index were Aggreko (-37p to 1022p), Booker Group (-7.2p to 205.1p), Investec (-17p to 558p), Drax Group (-11.1p to 370.8p) and Aberdeen Asset Management (-7.8p to 263.3p).