UBS cut its recommendation on the stock, while JP Morgan Cazenove trimmed its target price, a day after the Glasgow-based group posted a trading update.
Aggreko closed down 5.3 per cent or 92p at 1,660p, wiping more than £200 million off its market value.
The wider Footsie index closed down 25.39 points or 0.4 per cent at 6,348.82 as traders awaited the United States Federal Reserve’s decision on interest rates and bond buying, which came after the London market had closed.
David Jones, at IG Index said: “It being Fed day, investors are stuck doing their best ‘rabbit in the headlights’ impression, unable to move much for fear of being caught out.”
Since late last month, markets have been struggling to come to terms with the expected pull back in quantitative easing by the Fed.
London’s fallers yesterday included most of the major insurers, with Asia-facing Prudential down 19p at 1,068p, Edinburgh-based Standard Life 5.8p cheaper at 369.4p and Legal & General down 1.5p at 171.1p.
BT’s shares were under pressure as it announced that widely-respected Scots-born chief executive Ian Livingston will stand down in September.
Livingston, who is credited with sorting out the telecoms giant’s finances, is taking up a role in the UK government as a trade minister and will be replaced by BT Retail boss Gavin Patterson.
Shares were down as much as 4 per cent following the surprise announcement, but regained some of their losses to close down 5.6p at 313.7p.
NEW YORK: US stocks fell sharply last night, with losses accelerating after Federal Reserve chairman Ben Bernanke said the central bank could begin to scale back its stimulus measures later this year.
The Dow Jones industrial average was down 205.66 points, or 1.34 per cent, to close at 15,112.57 while the Standard & Poor’s 500 Index closed down 22.88 points, or 1.39 per cent, at 1,628.93. The Nasdaq Composite Index ended down 38.98 points, or 1.12 pecent, at 3,443.20.