Signs of a pick-up in support for Scottish independence left shares in Royal Bank of Scotland lower.
With RBS seen as being vulnerable to currency risks caused by a Yes vote, shares in the banking giant fell 2 per cent or 8.8p to 351.5p.
Lloyds Banking Group was down by a 1p at 74.8p and Perth-based energy company SSE was 25p cheaper at 1,329p.
But engineering firm Weir was the top of the FTSE 100 leaderboard after Credit Suisse upgraded its rating on the shares to “outperform”.
At the same time the broker cut its guidance on rival engineer IMI, saying Weir had a better profile and relative cash conversion. Weir lifted 67p to 2,706p, while IMI fell 25p to 1,329p.
The FTSE 100 Index gave back most of its early gains to close 3.86 points higher at 6,829.17, with housebuilders among those struggling.
Tony Cross, market analyst at Trustnet Direct, said: “Housebuilders came under pressure, despite strong construction sector survey, as interest rate concerns continue to trip-up investors in the sector.”
Barratt fell 6.4p to 362.4p and Persimmon slipped 2p to 1,331p. Redrow was 2.7p lower at 278.3p despite posting a 91 per cent jump in profits, as its sales rate has slowed in the new financial year due to the impact of new mortgage rules.
Miners were pushed higher on the back of a vote by the Australian government to scrap a tax on mining profits introduced two years ago. Rio Tinto climbed 5.5p to 3,236.5p and BHP Billiton was 15p higher at 1,920p.
Elsewhere, pub group JD Wetherspoon lifted 12.5p to 754.5p after analysts at Numis said strong sales but weak margins will see pre-tax profits rise slightly when the firm posts its full-year results next week.