THE SNP yesterday hit back at claims Scotland's charities were being used to engineer a second referendum question on greater devolution.

Nationalist MSP Stewart Maxwell accused Scottish LibDem leader Willie Rennie of being "illiberal and undemocratic" after he launched an outspoken attack on the Scottish Council for Voluntary Organisation (SCVO) and its chief executive Martin Sime.

Mr Rennie called on Mr Sime to resign after The Herald revealed private correspondence showing Alex Salmond's adviser Alex Bell helping the SCVO boss to build a case for a multi-question poll.

The LibDem leader claimed Mr Sime was allowing his organisation to be used as a "front" for a clandestine SNP Government move to have a fallback "more powers" option included in the referendum.

However, West of Scotland MSP Stewart Maxwell said: "This outburst from Willie Rennie is both illiberal and undemocratic.

"He is basically saying no-one should be allowed to have any debate or engagement on Scotland's constitutional future, unless they agree with the LibDems.

"The more the LibDems and other anti-independence parties try to silence any debate on the constitution, the more people in Scotland will be inclined to support independence."

The Herald revealed how Mr Salmond's political adviser alerted Mr Sime to a poll showing a majority of Unite trade union members wanted to see a second question on so-called devo-max.

The SCVO is the driving force behind the Future of Scotland group, a loose coalition of charities, churches, student groups and trade unions which is sympathetic to a wider range of options in the planned 2014 referendum.