Britain's main stock index inched higher on Wednesday led by gains in oil majors and miners, though investors remained cautious a day after lawmakers rejected Prime Minister Theresa May's revised Brexit deal.

The FTSE 100 was up 0.1 percent while the FTSE 250  was down 0.1 percent by 0940 GMT.

Oil heavyweights Shell and BP boosted the main bourse as oil prices rose on ongoing supply cuts from producer group OPEC and U.S. sanctions against Iran and Venezuela.

The index was also supported by Standard Life Aberdeen  which rose 3 percent, on track for its best day since early January, after posting full-year results and saying that it was doing away with a dual-CEO management structure.

Lawmakers voted against May's amended Brexit deal by 391 to 242 on Tuesday, forcing parliament to decide whether to back a no-deal Brexit or seek a last-minute delay to the process.

"This is all very messy - there is not clear and clean way out of this - leaving uncertainty and caution the order of the day for sterling and other UK assets," Markets.com analyst Neil Wilson said.

Parliament will vote later on Wednesday on whether to leave the bloc with no deal. If a no-deal exit plan is rejected, a vote on Thursday will decide whether to seek to extend the Brexit deadline.

"While this (extending the deadline) is something that might well be easy to achieve as it kicks the can down the road, it is by no means certain that the EU might feel obliged to accommodate it, if the reason behind the request doesn't have an endpoint goal behind it," said CMC Markets analyst Michael Hewson.

Gains on the main index were limited by a fall in financial and industrial stocks, as well as gambling firm GVC, which skidded 4.8 percent to its lowest level since June 2016.

Drugmaker Hikma shed 3.3 percent after lower-than-expected full-year profit and retailer Kingfisher  lost 1.8 percent after a Stifel downgrade.

Cyber security firm Avast dropped 4.5 percent to the bottom of the mid-cap index after its long-time CEO stepped down and it reported marginally lower-than-expected adjusted revenue and earnings in its first annual results since listing last May.

Outsourcing firm Capita fell 2.7 percent after it said late on Tuesday that Australia's Corporate Travel Management had made an unsolicited bid for its travel business.

But subprime lender Provident Financial, which has been subject to a hostile takeover by smaller rival Non-Standard Finance advanced 2 percent after it swung to a pre-tax profit in 2018.