At close,  the benchmark FTSE 100 index was down 27.47 points, or 0.4%, at 6,772.
The price of Brent crude slid fell 3.57% to $46.52 a barrel on worries that oil producers would fail to agree limits on output.
Shares in oil giants BP and Royal Dutch Shell were both down by about 2%.
Shares in UK housebuilders were trading higher on the back of stronger-than-expected mortgage lending figures.
Bank of England figures showed 67,518 mortgages were approved in October, a seven-month high.
Barratt Developments shares rose 2.28% while Persimmon climbed 1.95%.
Shares in BT Group saw big moves after telecoms regulator Ofcom ordered it to make its Openreach business legally separate.
BT shares fell 1.4% in early trade, but then recovered to stand about 1.16% higher by close.
Ofcom said BT had failed to voluntarily address competition concerns, adding it would notify the European Commission of its plans to force the legal separation of Openreach, which runs the UK's broadband infrastructure.
The regulator wants Openreach to become a distinct company with its own board, with non-executives and a chairperson not affiliated with BT. However, it has resisted calls to split Openreach off entirely.
"Ofcom isn't really saying anything radically different today in terms of the actual meat of the changes," said Neil Wilson, from ETX Capital.
"What's concerning investors is the detail of the separation, such as the transfer of pension liabilities and budget autonomy - BT's pension black hole has ballooned to top ??10bn and this is a concern for investors."
On the currency markets, the pound rose 0.64% against the dollar to $1.2497, and was 0.67% higher  against the euro at ???1.1774.
Oil companies weighed on the London market as energy shares were hit by a fall in oil prices ahead of the meeting of Opec oil producers on Wednesday.