Fears are growing that David Cameron's plans to use the G8 to battle tax evasion could end in disappointment, as it emerges that his most ambitious objectives are being opposed by other world leaders.
The Prime Minister wanted a new deal clamping down on those who illegally avoid tax to be the centrepiece of this year's summit, held in Lough Erne, Northern Ireland.
But while Downing Street insiders were hopeful of progress in today's crucial talks, they have encountered more opposition than expected.
The ongoing conflict in Syria is also threatening to overshadow the summit's scheduled discussions on trade, tax and transparency.
The UK came to the G8 summit with a double-barrelled plan. First, to establish and potentially publish new ledgers of so-called beneficial ownership, documenting those who profit from tax haven schemes.
Second, to create automatic information-sharing systems to ensure different countries can compare notes on how much tax certain individuals are paying.
While the UK expected to achieve further progress on this front at the G8, campaigners say the proposals risked being watered down, with the beneficial ownership registers kept private and with information-sharing not extended to developing countries.
The Prime Minister has had international tax evasion and avoidance at the top of his G8 agenda since he unveiled his programme at the World Economic Forum in Davos.
While the Lough Erne summit is focusing specifically on illegal evasion, the G20 summit in St Petersburg will examine avoidance - where people pay less tax than they ought to, while remaining within the law.
Chancellor George Osborne made an appearance at the summit this morning to explain the technical aspects of Britain's proposals, after which there was a full debate.
Although most other G8 members have expressed support for his plans, Russia, the US and Canada are thought to be comparatively lukewarm.
French president Francois Hollande has also undermined Mr Cameron by wondering aloud why the focus isn't on climate change.
The first day of the summit culminated in the official launch of the EU-US trade deal - the biggest bilateral set of trade negotiations in history.
The negotiations, which will take place over the course of the following years, are expected to yield hundreds of millions of dollars worth of extra economic growth to the countries involved.
Mr Cameron said they could create a £10bn-a-year windfall for the UK.