The US Labour Department showed 115,000 jobs were added in April, against expectations of 168,000, while a separate survey showed the unemployment rate edging down by less than expected to 8.1%.
The flight from risk meant the FTSE-100 closed 111.49 points lower at 5655.06 as the disappointing jobs stats caused global mining stocks to fall.
Big fallers included Chilean miner Antofagasta, which was down 36p to 1072p, while Kazakhmys was off 51p at 774p.
The pound was worth 1.61 dollars after a 0.2% fall while it was marginally stronger against the euro at 1.23.
The disappointing jobs figures diverted attention from hopes that first-quarter results from RBS will help to hasten the sale of the Government's 82% stake in the NatWest owner.
Chief executive Stephen Hester said there had been progress in "removing the mistakes of the past" as the group reported an operating profit of £1.1 billion.
Shares were up by as much as 3% at one stage but closed 0.1p lower at 24.5p.
Lloyds Banking Group held firm – up 1p to 32.6p – after its own largely positive message earlier this week but HSBC, which reports first-quarter figures on Tuesday, was down 8.2p at 555.1p.
Supermarkets had a mixed session despite Waitrose reporting a 10.7% rise in sales in the week to last Saturday.
Morrisons, which endured a difficult session on Thursday after its first reversal in like-for-like sales since 2004, lost initial gains and stood 1.3p lower to 275.2p, while Sainsbury's shed 2.8p to 305p. Tesco, however, was one of only four top flight risers as it lifted a penny to 319.2p.
Rentokil Initial's troubled turnaround of City Link continued to weigh on the pest control firm after the division posted quarterly losses of £12.7 million.The shares fell 3.45p to 83.15p.
There was better news from retailer HMV, whose shares jumped 12%, or 0.45p, to 4.15p as it forecast a return to profit next year, countering City expectations for a £5m loss.
The biggest FTSE-100 risers were Lloyds Banking Group up 1p at 32.6p, Weir ahead 19p at 1635p, Tesco up 1p to 319.2p and International Power ahead 0.3p at 417.7p.
The biggest fallers were Kazakhmys down 51p at 774p, Eurasian Natural Resources off 33p at 520p, Tullow Oil down 88p at 1469p and Man Group off 4.7p at 88.75p.