Former Prime Minister Gordon Brown has criticised plans for a citizens' assembly in Scotland, claiming they "lack ambition".

He praised the Scottish government for deciding to hold the assembly but warned it will not work if its terms of reference focus narrowly on Scottish independence.

The former Labour leader is an advocate of citizens' assemblies and believes they can fill a gap in the political system.

Earlier this week, the Scottish Government said 120 members of the public will be selected at random to serve on the assembly, with meetings held on six weekends between this autumn and spring 2020.

The three issues under consideration are: what kind of country Scotland should be; how it can overcome challenges including those arising from Brexit; and what further work is required to enable people to make informed choices on Scotland's future.

Writing in the Scotland On Sunday newspaper, Brown said: "Whether or not there is a future independence referendum, citizens' assemblies offer us the chance to have a more informed debate about the key issues affecting our economic and social future.

"But while the Scottish Government deserves credit for taking up the assembly idea, their current proposals - one citizens' assembly of 100 meeting six times - lack ambition.

"The better approach would be assemblies in every major region of the country - perhaps half a dozen - with 100 citizens in each.

"An online community of several hundred could be added to engage a wider number of citizens at little extra cost and with not 100 but 1,000 participating, the exercise would be far more inclusive.

"But the assemblies will not be seen as legitimate if their terms of reference are so narrow that all they do - as one independence supporting MSP suggested - is 'to debate the Yes/No question in a future referendum'.

"Indeed they would miss out on so much that matters in people's lives if they restricted the discussion to the constitution."

An SNP spokesman said: "We welcome Gordon Brown's support for citizens' assemblies."