Alex Salmond is seeking the help of Dr Ian Paisley to help him wrest more tax raising powers for Scotland from Gordon Brown.
Salmond will fly tomorrow to Belfast for meetings with Paisley, the DUP first minister, and Martin McGuinness, the Sinn Féin deputy first minster, to discuss how the two devolved governments win control of corporation tax from the Treasury and set their own low rates.
The visit is the first step in Salmond's plan to unite the leaders of Scotland, Wales and Northern Ireland in order to confront Gordon Brown with joint demands when he is prime minister.
The intitial request will be to revive a series of mothballed joint ministerial committees between the regions and Whitehall, in which cabinet secretaries would thrash out cross-border issues, with an annual meeting of the three first ministers and the prime minister.
After establishing the formal framework, Salmond intends to push for more financial powers for the Scottish parliament, with corporation tax a priority.
The SNP government wants to cut the rate from 30% to 20%, while the Northern Ireland government has argued that, as part of the peace process, it should have parity with the Irish Republic, where the rate is 12.5%.
Long-term, Salmond wants to push for fiscal autonomy, where Holyrood would set and collect all the taxes it spends instead of relying on a Treasury grant.
"The argument that the competitive position of Northern Ireland and Wales and Scotland must be transformed is hugely important. Corporation tax is a mechanism to do that," said a source close to the first minister.
"Once the principle is conceded by the United Kingdom Treasury of allowing that flexibility in taxation regimes, then that concession is our opportunity to establish it for Scotland.
"Our solution might lie along the line of fiscal autonomy."
Scottish, Welsh and Northern Irish environment ministers will tomorrow meet their UK counterpart, David Miliband, in London to discuss climate change.
On Thursday, finance secretary John Swinney will tell MSPs the timetable for a new bill to cut carbon emissions from businesses, homes and transport.
The bill, which is expected out next year, will set an annual target for cutting carbon emissions of 3%, with an 80% cut by 2050.
The targets are higher than those being considered by Westminster, as Scotland's wilder landscape and coast have the potential to generate more wind, wave and tidal energy.