A surprise decision by UK Prime Minister Theresa May to call a general election and declining iron ore prices sent both major London indices lower on Tuesday (18 April), as trading resumed following the Easter holiday weekend.
At 4.06pm BST, the FTSE 100 was down 2.24% or 164.27 points at 7,163.32 while the FTSE 250 was 1.09% or 212.92 points lower at 19,527.22. Earlier May had called an election for 8 June, asking the British public for a stronger mandate ahead of Brexit talks with the European Union.
With mining stocks already reeling from a 5% decline in iron ore prices to a near six-month of $61.50 per tonne, May's decision and a subsequent strengthening in the value of the pound clobbered the market.
Glencore (-4.90%), BHP Billiton (-4.85%) and Anglo American (-4.06%) were among the biggest fallers on the FTSE 100, with BP (-3.51%) and Johnson Matthey (-3.48%) in close proximity.
However, housebuilders Barratt Developments (+1.30%), Taylor Wimpey (+0.61%) and Persimmon (+0.59%) bucked wider market declines to post modest gains.
Laith Khalaf, senior analyst at Hargreaves Lansdown, said the rising pound helped heap pressure on the UK stock market, which was already on the back foot thanks to declining iron ore prices hitting the resources sector.
"Markets can get a case of the jitters in the run up to elections, but this one may be different as it comes in the wake of the Brexit vote, and the polls suggest the incumbent government is likely to remain in power and gain more seats.
"Nonetheless a snap election does potentially open the door to some market volatility in the coming months, though investors shouldn't let their investment decisions be dictated by swaying polls."
On FTSE 250, miner Ferrexpo (-9.87%) was the biggest faller of the session with sector peers Vedanta Resources (-7.23%), Evraz (-5.76%) and Acacia Mining (-5.13%) joining its ranks on the fallers' roster.
As with the large caps, midcap real estate companies Bovis Homes and Capital & Counties Properties were among the gainers, notching upticks of 1.65% and 1.52% respectively.