A slowdown in UK construction expansion and downgrades to Eurozone growth forecasts hit UK stocks on Tuesday morning, with the FTSE 100 having erased early gains by lunchtime.Well-received results from Imperial Tobacco, Associated British Foods and Legal & General weren't enough to prop up the benchmark index, which was being weighed down by heavy falls in the energy sector as oil prices dropped.The FTSE 100 was 0.2% lower at 6,477 by midday.Data released during the morning by Markit and the Chartered Institute of Purchasing & Supply showed that British construction output expanded last month at its weakest rate since May, compounding fears that the UK economic recovery is losing steam. The UK construction purchasing managers' index (PMI) registered 61.4 in October, down from 64.2 in September mainly due to a sharp fall-off in house-building, though it still remains firmly above the neutral 50-point mark.Also weighing on sentiment was the news that the European Commission has lowered its forecasts for gross domestic product (GDP) growth in the Eurozone for this year and the next. Euro-area GDP is now expected to expand by just 0.8% and 1.1% in 2014 and 2015, compared with its previous forecasts in May of 1.2% and 1.7% respectively.Meanwhile, oil stocks were tracking the price of crude lower as West Texas Intermediate (WTI) fell to a three-year low. Saudi Arabia lowered prices for crude exports to US customers ahead of US government data due out on Wednesday which is expected to show that stockpiles rose by 1.9m barrels last week. WTI futures were down as much as 2% at $77.20 a barrel on Tuesday, a level not seen since October 2011.Oil stocks fall, but earnings impressOil and gas producers Tullow Oil, Shell, BP, BG Group, Premier Oil, Afren, Cairn Energy and Ophir Energy were among the worst performers on Tuesday as stocks tracked oil prices lower. Oil services peers Hunting and Petrofac were also out of favour.Cigarette maker Imperial Tobacco gained as it hailed rising demand for key brands such as Davidoff, JPS and Lambert & Butler and said it it was boosting its annual dividend by 10% to 128.1p a share.Full-year earnings and dividends from Associated British Foods were up 6% on the prior year despite revenues falling 3%. Shares were higher after the company reported a "magnificent" year for its Primark clothing chain where operating profits jumped 30%.Insurance and pensions group Legal & General also rose after saying it racked up record annuity sales of £3.9bn in the first nine months of the year despite British government changes that have relaxed obligations on people to buy annuities to save for their retirement.Spirit Pub Company was in demand after British brewer and pub group Greene King made a firm £773.6m takeover bid, upping the pressure on rival suitor C&C. Market MoverstechMARK 2,761.21 -0.16%FTSE 100 6,476.95 -0.17%FTSE 250 15,461.17 +0.05%FTSE 100 - RisersImperial Tobacco Group (IMT) 2,761.00p +3.52%Randgold Resources Ltd. (RRS) 3,813.00p +3.05%Associated British Foods (ABF) 2,732.00p +2.28%Mondi (MNDI) 1,065.00p +2.01%Legal & General Group (LGEN) 235.00p +1.91%Fresnillo (FRES) 706.50p +1.65%Marks & Spencer Group (MKS) 410.20p +1.56%Schroders (SDR) 2,426.00p +1.51%British Land Co (BLND) 730.50p +1.46%Ashtead Group (AHT) 1,048.00p +1.45%FTSE 100 - FallersTullow Oil (TLW) 467.60p -3.25%Aggreko (AGK) 1,473.00p -3.09%Petrofac Ltd. (PFC) 1,047.00p -3.06%BG Group (BG.) 1,010.00p -2.51%Royal Dutch Shell 'B' (RDSB) 2,228.00p -2.37%BP (BP.) 434.50p -2.07%Royal Dutch Shell 'A' (RDSA) 2,151.00p -2.05%Weir Group (WEIR) 2,207.00p -1.52%Burberry Group (BRBY) 1,489.00p -1.33%BAE Systems (BA.) 451.70p -1.31%FTSE 250 - RisersMan Group (EMG) 128.00p +3.73%Thomas Cook Group (TCG) 129.20p +3.28%NMC Health (NMC) 500.00p +2.61%Crest Nicholson Holdings (CRST) 341.40p +2.46%RPC Group (RPC) 545.00p +2.35%Tullett Prebon (TLPR) 288.70p +2.05%African Barrick Gold (ABG) 212.20p +2.02%IG Group Holdings (IGG) 614.50p +1.99%Unite Group (UTG) 434.80p +1.99%Essentra (ESNT) 702.50p +1.96%FTSE 250 - FallersJardine Lloyd Thompson Group (JLT) 883.00p -6.06%Premier Oil (PMO) 244.50p -4.72%Ophir Energy (OPHR) 181.30p -4.53%Afren (AFR) 71.80p -4.46%Cairn Energy (CNE) 141.80p -4.38%Hunting (HTG) 704.00p -3.96%Amec (AMEC) 1,015.00p -3.88%Greene King (GNK) 778.50p -3.71%Regus (RGU) 188.40p -3.38%Wood Group (John) (WG.) 645.00p -3.01%