By Glenn Campbell Political correspondent, BBC Scotland

Robin Harper, Green co-convener, would be involved if talks take place

The Scottish Executive's permanent secretary normally meets leaders from the largest opposition parties.

Ahead of the next Holyrood elections, Sir John Elvidge may extend that courtesy to smaller parties.

The executive said the permanent secretary had not yet decided who to invite for talks but added that his plans were being "kept under review".

Green MSP Mark Ballard told BBC Scotland: "We fully expect them to extend discussions to the Greens.

"There's a real possibility of Greens holding the balance of power after next May's elections."

Power-sharing

Civil servants have to be even handed and work impartially for whichever political parties win power.

Ever since devolution Labour and the Liberal Democrats have been their political masters.

But the administrators have to prepare for the possibility of a change.

Prior to the Holyrood elections in 1999 and 2003, the executive's top civil servants met with leaders from the Scottish National Party and the Conservatives.

It allows opposition parties to brief civil servants on their plans for government.

Alex Salmond has failed to explain how is he going to fill the �11bn black hole at the heart of his plans to divorce Scotland from the rest of the UK Labour Party spokesman

Since the last election, Holyrood has MSPs from seven political parties and a handful of independents.

This fragmentation of political support makes new coalitions possible and increases the chances of smaller parties becoming king-makers.

It has already emerged that Greens have held talks with the SNP about the possibility of power-sharing at Holyrood.

Buoyed by recent opinion polls, SNP leader Alex Salmond has written to the permanent secretary to request the start of pre-election contacts.

The executive said they would happen "nearer the time" of next May's election, possibly in January.

The SNP wants to discuss its programme for the first 100 days of an SNP-led administration.

The party's plans include scrapping the graduate endowment, overhauling Scottish Enterprise and a bill to pave the way for an independence referendum.

Mr Salmond said he would like to "hit the ground running" as first minister by making St Andrews Day a public holiday.