But Sir Reg, who met the Conservative leader yesterday morning, said that the DUP was doing little to endear itself to the man who looks increasingly likely to be the next Prime Minister.

The escalating economic crisis meant that Mr Cameron cancelled a series of engagements and delivered an unscheduled speech to the conference about the grave financial upheaval stalking the globe.

But the meeting between Mr Cameron and senior Ulster Unionist strategists went ahead and Sir Reg said that the Conservative leader had made clear that the Union is central to his agenda for any future Tory government.

"We had a chat and it is very clear that he is committed to the Union – not just in a passive way but in a proactive way," he said.

"We didn't go into a lot of detail today – that is for the working group – but it was a stock-taking exercise."

Sir Reg said that the DUP was becoming "irrational" in its continued attacks on the UUP-Conservative talks about possible electoral cooperation.

Relations between the DUP and the Conservatives have become increasingly strained following the DUP's last-minute decision to back Gordon Brown in the Commons vote on 42-day detention.

In the seconds after the vote was announced, Strangford MP Iris Robinson held up nine fingers to Tory MPs, an act of defiance which enraged the Conservative benches.

And, in the latest DUP attack on the talks, Jeffrey Donaldson told a fringe meeting at the conference on Monday that the Conservatives and Ulster Unionists would be splitting the unionist vote if they stood against the DUP.

But Sir Reg responded: "There has been such reaction from the DUP to the talks and such an irrational response from them.

"Jeffrey Donaldson came over here yesterday and spent some of his time slagging off his own hosts which didn't leave a very good impression.

"How can he lecture us about splits when he left the UUP over power-sharing with Sinn Fein yet now is a Junior Minister with Gerry Kelly?"

It is understood that Mr Cameron will soon visit the Province for further meetings with the UUP.

Aside from the acrimony over the UUP talks, DUP education spokesman Mervyn Storey yesterday met with his Conservative counterpart Michael Gove at the conference.

Mr Storey said that Mr Gove had shown a "strong interest in the DUP analysis of the ongoing debate about the future of education in Northern Ireland" and had agreed to further meetings.