Media playback is unsupported on your device Media caption BP boss Bob Dudley: "Great Britain is great and it ought to stay together"

Oil giant BP boss Bob Dudley has warned there are "big uncertainties" for the company over the possibility of Scotland becoming independent.

Mr Dudley told the BBC the "question mark" over which currency Scotland might adopt if there was a 'yes' vote in September's referendum was "a concern".

However, Mr Dudley emphasised the firm was continuing to invest in Scotland.

Separately, BP reported a fall in profit for 2013.

Analysis Businesses don't vote, but their leaders' opinions could be influential in the Scottish referendum on independence. The response from most of them is to keep quiet, not least to avoid alienating customers or ending on the wrong side of the result, as some leading figures did in the 1990s devolution debate. Many are relying on their trade bodies to ask questions about the implications of the SNP Scottish government's independence plans. There are some in business openly supporting either side. Among them, the 'Yes Scotland' campaign probably draws most support from small businesses and entrepreneurs. The comments from BP's Bob Dudley follow efforts by the Scottish government to ensure the oil and gas sector is reassured that the only changes it might see from independence would be positive. The sector is far too important to Scotland's economic future for the Scottish National Party to alienate it.

BP plans to invest £10bn in the North Sea between 2011 and 2016, its highest ever investment in the region.

"We have a lot of people in Scotland. We have a lot of investments in Scotland. My personal view is that Great Britain is great and it ought to stay together," added Mr Dudley.

Alistair Darling, head of the Better Together campaign, said Mr Dudley's comments marked the biggest intervention by a major business so far in the referendum debate.

"I hope that more companies and business leaders speak out over the coming weeks and months. This debate is far too important to be left to politicians alone," he added.

However, the pro-independence Yes Scotland campaign dismissed Bob Dudley's remarks.

"With independence, the continued use of sterling has the overwhelming support of the people of Scotland and the public in the rest of the UK," a spokesman said.

Scotland's first minister, Alex Salmond, said that Mr Dudley was "entitled to his personal opinion" but added that many other chief executives were firmly in favour of independence. He said he would "continue to co-operate" with BP.

Image copyright AFP Image caption The Deepwater Horizon rig explosion caused the worst spill in US history

Profit slips

Meanwhile, the firm said that underlying replacement cost profit - which strips out one-off gains and the effect of oil price movements - was $13.4bn (£8.2bn) last year, down from $17.1bn in 2012.

BP said lost income from asset sales, weaker margins on refining and higher exploration write-offs were to blame.

In the 1979 referendum, the business sector played a significant role in casting a shadow of doubt over the then proposals for devolution. Brian Taylor, Political Editor, Scotland Read more from Brian Taylor

For the final three months of last year, BP said underlying replacement cost profit fell to $2.8bn from $3.9bn.

The result for the third quarter was just above average analyst forecasts for $2.7bn.

Including the impact of the asset sales and one-off gains, BP said replacement cost profit for the year more than doubled to $23.7bn compared with $11.4bn in 2012.

This was largely thanks to the one-off gain from BP's $17bn sale of its interest in the joint venture TNK-BP, which it sold to Russia's Rosneft.

'Transformation under way'

BP has sold off $38bn worth of assets since the Deepwater Horizon oil spill in the Gulf of Mexico, helping it to fund compensation payouts.

However, this sell-off has hit production. BP said it expected reported production to be lower in 2014 due to the sales.

The oil firm said in October it still plans to sell off a further $10bn worth of assets by the end of next year.

Richard Hunter, head of equities at Hargreaves Lansdown Stockbrokers, said BP's results were in line with expectations and its transformation into "a more lean and focused business is well under way".