Lingering Brexit concerns have left sterling hamstrung on,boosting firms with a larger international exposure such as Shell, Unilever and Diageo, which lent further support to the main index.
The pound fell to a low of $1.293, down 0.6% on the day.
It was also 0.6% lower versus the euro at 85.8 pence, hitting its lowest level in over three weeks.
"The direction of last few days has been downward as the market is concerned about post-Brexit negotiations but one wouldn't draw too many conclusions about today's moves as liquidity is poor," said Stephen Gallo, European head of FX strategy at BMO Capital Markets in London.
