THE Scottish National Party is expected to endorse a plan tomorrow to forge a political alliance with the Greens in the European Parliament for the next five years, writes European Correspondent Rory Watson.

The idea has already won the support this week of the 38 Green MEPs elected in last month's Euro-elections. It must now be formally approved by the SNP's national executive when it meets in Edinburgh this weekend. The deal also needs clearance from Plaid Cymru in Wales, various autonomous parties in Spain , and from the moderate Flemish nationalist party Volksunie in Belgium.

SNP officials insisted last night that the alliance was only one of three options facing the two SNP MEPs and their seven colleagues from similar autonomist political parties in Europe. There is also the possibility of linking up with a small group of Italian radicals or of constructing a loose association of regionalist and left-of-centre MEPs.

But there is little doubt that a partnership between the SNP and the Greens, which would still leave each free to campaign and vote on its own manifesto pledges, would give the nationalists more clout in the 626-member Parliament. It would make the group the fourth largest, after the Liberals, Socialists and Christian Democrats and give it a better chance of securing some high-profile posts.

One Green official said yesterday: ''For us, the deal is done,'' and confirmed that the new political group would be called The Greens/European Free Alliance.

Green MSP Robin Harper said: ''If the SNP join the Green group in Europe, they will lend support to Green policy for Europe. The two parties will still be free to go their own way in Scotland.''