By Shashwat Awasthi and Yadarisa Shabong
(Reuters) - Heightened concerns over the course of Brexit and mounting pressure on Prime Minister Theresa May to step down weighed heavily on Britain's mid-cap index and domestically-focused blue-chip stocks on Thursday.
As the pound fell, the FTSE 250 lost 1.4% to hit its lowest point since March 29, when Britain was originally scheduled to exit the European Union. Dublin's main index, often regarded as a barometer of Brexit jitters, was also down nearly 1.4%.
May's final attempt to muster parliamentary support for a divorce deal on Wednesday sparked a fierce backlash by some of her Brexit-supporting ministers. The turmoil was compounded when prominent Brexit supporter and Leader of the House of Commons, Andrea Leadsom, resigned from the government.
This cast further uncertainty over Britain's political scene and sparked a sell-off in sterling, amid speculation that other ministers could also quit, and re-emerging fears of a "no-deal" Brexit after May is replaced.
"For sterling it will depend entirely on what, or rather who, is next (as UK prime minister). In the interim we should expect volatility in sterling crosses to remain elevated," Markets.com analyst Neil Wilson said.
Britain-focused banks and industrial stocks on the FTSE 100 were also hit as the index fell 1.4%, though sterling's slide helped its exporter stocks gain despite lingering global trade concerns.
As May's premiership hung in the balance, Royal Mail skidded 10.3% to a record low on the mid-cap index.
"There is a very slight risk that with Theresa May in turmoil a (Jeremy) Corbyn government is more likely and he would nationalise businesses like Royal Mail," a trader said.
Oil majors were the biggest drags on the FTSE 100 as unresolved Sino-U.S. trade tensions hit demand outlook and pressured oil prices. [O/R]
Shares of TUI fell 4.8% to the bottom of the main bourse after a survey by Barclays showed more Britons would opt for "staycations" this year over heading for trips abroad, with many citing the impact of Brexit on travel and finances.
Mid-cap outsourcing firm Serco jumped 7.4% on its best day in more than five months, after saying it would buy U.S. Navy supplier Alion's Naval Systems Business Unit.
Madame Tussauds-owner Merlin Entertainments advanced 7.5% after hedge fund ValueAct urged it to explore a go-private deal, calculating the move could boost the company's value by around a third.
(Graphic - FTSE on track for monthly loss but outperforms STOXX 600, https://tmsnrt.rs/2YH6l69)
(Reporting by Shashwat Awasthi and Yadarisa Shabong in Bengaluru; Editing by Mark Heinrich)