Nicol Stephen has not ruled out working with the SNP

Speaking at the party's UK conference, Nicol Stephen said the Lib Dems would become the biggest party at Holyrood.

Earlier, he said his party could only work with the SNP if it abandoned its "blocking" policy of an independence referendum.

However, Mr Stephen said he has never ruled out working with other parties.

In his speech to delegates in Brighton, the deputy first minister said the party could jump from fourth to first at the Scottish Parliament elections.

He pointed to the Lib Dems' massive by-election victory in Dunfermline and West Fife earlier this year, saying "in becoming Scotland's largest party, we will gain seats from the SNP as well as Labour."

Mr Stephen claimed the Lib Dems had proved they could deliver in coalition with Labour and would do so alone in power, with a radical, reforming and responsible agenda.

That block is called separatism and it's called the referendum Nicol Stephen Scottish Liberal Democrat Leader

On Monday, SNP leader Alex Salmond accused the Lib Dems of "cosying up to Labour" after Mr Stephen said his party was "clearly opposed" to an independence referendum.

Mr Stephen said the SNP's referendum policy was a "block" to working with others.

Denying he was ruling out a deal, Mr Stephen said: "It's a question you might want to put to Mr Salmond about why he is putting one policy against all those other policies that the SNP talk about week in, week out, in the parliament.

"But it seems in terms of schools, hospitals, local income tax and areas where we could agree, Alex Salmond doesn't want to have a conversation because he wishes to put a block in the way of it.

"And that block is called separatism and it's called the referendum."

He listed his party's key policy areas like renewable energy, education and a pro-enterprise economy.

Mr Stephen has pledged that all of Scotland's electricity would be generated by renewable sources by 2050, if his party emerged victorious.

Alex Salmond says the Lib Dems are "cosying up to Labour"

He added that an independence referendum would cause "complete constitutional turmoil" and he did not want the Lib Dems to be a "stepping stone for independence".

Mr Stephen later told the conference he wanted to scrap a party rule that said it had to speak first to the largest party in any coalition talks.

Mr Salmond attacked the Lib Dems saying it was the SNP making major gains in opinion polls.

He added: "We know that next year's Scottish election is a straight fight between the SNP and Labour."

Also at the conference, Lib Dem leader Sir Menzies Campbell won a crunch vote on his tax plans.