ROYAL Mail ended the day rock bottom of the FTSE 100 for the second session in a row, helping drag the index into the red.
Investors continued to fret over the delivery firm's performance following a shock profit warning issued on Monday afternoon.
The group said that a target for cost avoidance has been slashed from £230 million to £100m as it cautioned that adjusted operating profit will come in between £500m to £550m, compared with £694m last year.
Shares in Royal Mail closed down 32.8p, or 8.38%, at 358.6p, capping another bruising day's trading for the firm.
London's top flight ended the day down 21.12 points, or 0.28 per cent, at 7,474.55.
Also in the doldrums was Ferguson, despite cheering a 15% hike in annual profits as another strong performance in its US business offset "tough" UK trading.
The group, formerly known as Wolseley, reported trading profits of $1.5 billion (£1.2bn) for the year to July 31, up 15.3% or 14.7% higher with currency movements stripped out.
Trading profits in its US business, which now accounts for 90% of earnings, jumped 16.8% higher to $1.4bn (£1.1bn).
But shares closed down 446p at 6,083p.
Russ Mould, AJ Bell investment director, said: "Investors' concerns seem to focus on the UK and a comment about September's sales growth rate coming in a little below that of August."
Shell and BP were among the risers as they rode the wave of rising oil prices. Despite nudging down on Tuesday, the price of a barrel of Brent crude has risen from $77 to $84 over the past 30 days.
Shares in Shell and BP closed up 7p at 2,655.5p and 1.7p at 597p respectively.
Sterling, meanwhile, remained hostage to Brexit ruminations as the Tory party conference rumbles on.
The pound was down 0.4% versus the US dollar at 1.298 and down 0.3% against the euro at 1.123.
It was also dragged down by lacklustre construction figures, which showed the sector suffered its weakest growth for six months in September
The closely-watched Markit/CIPS UK Construction purchasing managers' index (PMI) showed a weaker-than-expected reading of 52.1 in September down from 52.9 in August
However, as Theresa May prepares to deliver a speech Wednesday, focus will again shift to politics.
"For sterling the problem is, to the surprise of no-one, Brexit.
"Uncertainty surrounding Britain's EU divorce led the construction sector to grow at its slowest pace for six months, contributing to the currency's decline in the process, while the pound is also jittery ahead of Theresa May's Tory Party conference speech on Wednesday morning.
"What tone the Prime Minister strikes in regards to Brexit could well dictate sterling's performance across the rest of the week, hence the pre-game nerves on Tuesday," said Connor Campbell, financial analyst at SpreadEx.
In Europe, Germany's DAX was down 0.42% and France's CAC fell 0.71%.
The biggest risers on the FTSE 100 were United Utilities up 14.8p at 719.6p, Randgold Resources up 100p at 5,518p, Evraz up 9.8p at 578p and BHP Billiton up 28p at 1,698.4p.
The biggest fallers on the FTSE 100 were Royal Mail down 32.8p at 358.6p, Ferguson down 446p at 6,083p, Pearson down 34.4p at 854p and Johnson Matthey down 120p at 3,476p.
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