The pro-independence campaign has unveiled Chris and Colin Weir as its biggest backers, along with thousands of friends giving fivers. But is it struggling to find other well-heeled fans?

The pro-independence campaign by Yes Scotland has been heavily funded by the UK's largest Euromillions jackpot winners, Chris and Colin Weir, who have given the group £1m towards its first seven months of operation.

And they may continue to do so: the Weirs, who collected a record £161m jackpot in July 2011, have told Yes Scotland they will donate again if needed. And their money may yet prove essential.

The couple, both active nationalists who have already given £1m to the Scottish National party, each donated £500,000 to Yes Scotland, the largest sums within the £1,625,797 declared in Yes Scotland's first list of financial backers on Wednesday.

The list confirmed that the SNP has kept back all the money donated to it by both the Weirs in November 2011 and the £918,000 given it by the estate of the Scots makar (or national poet) Edwin Morgan in June 2011, to support its own hefty campaigning costs.

Even so, the SNP does emerge as the next largest backer for Yes Scotland, but not with cash. It gave £342,767 in kind by funding all its initial start up costs, the Yes Scotland launch rally in Edinburgh in early 2012, and its early staffing costs, before its formal launch on 1 September.

In contrast to the pro-UK Better Together coalition, which is now weathering attacks over the provenance of some of its finance after disclosing its £1.12m in donations on Sunday, Yes Scotland is short of wealthy benefactors and relies on a small pool of well-heeled friends.

Its next largest cash donations were £250,000 from Angus Tulloch, a funds manager in Edinburgh, £25,000 from builder Alexander Adam, whose Springfield Properties HQ was opened by Environment secretary and local MSP Richard Lochhead recently, and £8,000 from William Wilson, who owns a chain of pharmacies in Glasgow.

The remainder of that £1.6m – some £112,000 - came from 7,000 small donations, only a minority of which were larger than £500 it seems. Yes Scotland would not provide a breakdown of gifts below £7,500, saying as so many were bank notes stuffed into collection boxes at rallies, the administrative burden of listing each was too great.

We've had so many very, very small donations from public meetings, like fivers here and tenners there.

This raises questions about Yes Scotland's long-term financing: its officials already intimate they expect Better Together to be better-funded. We know of Nicola Sturgeon's anxieties that independence might be defeated by English gold. Might the Weirs, who have already given away millions from their lottery windfall, continue backing Yes Scotland?

Their spokeswoman said:

If the Yes Scotland campaign identifies a need for further funds, Mr and Mrs Weir would consider it.

She added:

Chris and Colin Weir's lifelong commitment to independence is well known. Their donations to this cause are in line with their financial means and reflect their desire to see a level playing field for this important issue to be debated fully and fairly.

The Weirs and Adam donations seem influenced, in part at least, by their personal connections with Yes Scotland chief executive Blair Jenkins. While privately campaigning and even standing for the SNP, Colin Weir was also a cameraman for STV where Jenkins was its head of news. They are personal friends; Jenkins also apparently knows Adam - they both hail from Elgin.

Noticeably absent from the Yes Scotland ledgers are some of the SNP's wealthiest and best known backers. Sir Sean Connery is excluded because he lives abroad (Yes Scotland also refuses gifts above £500 from donors outside Scotland), but where, asked the Sunday Herald's Tom Gordon on Wednesday morning, are the likes of Stagecoach group millionaire Sir Brian Souter?

Tom Gordon (@ScottishPol) Brian Souter conspicuously absent from list of .@yesscotland donors >£7.5k #indyref twitter.com/ScottishPol/st…

Better Together's chief executive Blair MacDougall said these donations established that Yes Scotland was effectively bank-rolled by confirmed nationalists close to the SNP, and was not the broad-based movement it claimed to be.

That charge was rejected by Jenkins: he said thousands of ordinary Scots had donated money, nearly all of which originated inside Scotland. He admitted some smaller sums – about 1% of the total - had come from overseas, chiefly from expats.

He insisted Yes Scotland would only take sums over £500 from Scottish voters – a pointed reference to Better Together's decision, which is entirely consistent with the Scottish government's proposed rules on referendum spending, to take money from any UK voter. Jenkins said:

We believe the appropriate position is that both campaigns should agree that any donation above £500 – the legally recognised level over which money given becomes a "donation" – should come only from those registered to vote in Scotland's referendum. Yes Scotland is sticking firmly to that.

Meanwhile, Better Together's opponents have retaliated by attacking the business dealings of its biggest benefactor, Ian Taylor, millionaire chief executive of the Geneva-based oil trading firm Vitol. A substantial personal donor to the Tory party and to the Harris tweed industry, Taylor – a Scot who lives in London - gave Better Together its largest single gift: £500,000.

As this blog reported on Monday, Vitol has faced critical questions about its dealings with Libyan rebels, Serbian warlords, with Iran oil sales and with Saddam Hussein's Iraq.

First reported by the pro-independence website National Collective, The Herald on Wednesday listed a series of cases where Vitol had hit controversy, including a $1m payment to the Serbian warlord Arkan in the 1990s, who was indicted at the Hague for crimes against humanity, and for allegedly paying "kickbacks" on oil deals with Saddam Hussein's Iraq, which a New York court found undermined the UN oil for food programme, and had "admitted" buying and selling Iran, ignoring international sanctions.

Vitol also helped supply fuel, through Qatar, to the Libyan rebel movement which toppled Muammar Qaddafy's regime with Nato air and tactical support – a strategy which was also backed by the SNP. However, allegations this deal was brokered with help from Tory minister Alan Duncan, or the Foreign Office, are vigorously denied by Vitol:

Any suggestion that there's a cosy deal here isn't true.

Angus Robertson MP, the SNP's Westminster leader, insisted these issues were so serious Alistair Darling, the chairman of Better Together, who personally brokered Taylor's donation on Lewis last year, should firstly hand the money back and then investigate. He stated:

This information is extremely serious, and raises urgent questions which Alistair Darling must answer. The No campaign must return this money immediately pending full answers to these questions.

Vitol has retaliated, asserting that many of the claims against it are untrue and libellous; the Herald has now had a lawyer's letter and so too has National Collective. The pro- independence site has now taken its article offline: the page now reads "not for publication".

Brunswick, Vitol's PR firm, said:

The company has taken legal advice and will take whatever steps are deemed necessary to have these inaccuracies corrected, and to prevent their further publication.

It said its dealings in Serbia had been legal and never the subject of government or legal sanction; on Iraq it admitted paying fines, restitution and costs totalling $17.5m, along with other major oil firms, but insisted its payments to Iraq's state oil company (SOMO) were surcharges it had demanded, and were "neither bribes nor kickbacks"; it denied ever breaching sanctions on Iranian oil sales, but confirmed a subsidiary on Bahrain had bought an oil consignment on the open market of Iranian crude. It was via a third party, but would not do so again, Vitol said, and insisted it had banned deals with Iran before international sanctions were in place.