The co-leader of the pro-independence Scottish Greens wants everyone resident in Scotland, aged 16 and over, to have the right to vote in a second independence referendum.
Patrick Harvie said while he welcomed new legislation to enable a second referendum, the number of people eligible to vote should be expanded.
The Referendums (Scotland) Bill, which was published by Nicola Sturgeon's government today, states that the franchise in any new referendum would be the same as that in Scotland's council and Holyrood elections. The Bill specifies that voters would have to be aged 16 and over and a UK, Commonwealth, Republic of Ireland or EU citizen.
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But the Scottish Government had previously said that it would look to extend the voting franchise to "everyone legally resident in Scotland", after Holyrood was granted new powers over the running of elections in 2016.
That would mean anyone living in Scotland, aged 16 and over, including those granted asylum or a visa, would be able to vote in Scottish elections - including referendums.
Today Patrick Harvie MSP said that while he welcomed the new Bill those who were allowed to vote in it should not be restricted by citizenship.
He said: “The detail of the Bill needs scrutiny, like the inclusion of a citizenship requirement for the right to vote, despite repeated promises by the Scottish Government to ensure that voting rights are based on residency instead."
Last year the then SNP parliamentary business manager Joe FitzPatrick said there was a "view" that the current rules on who could vote did not reflect modern Scotland and “that linking citizenship with the right to vote is undemocratic”.
He added: “As citizens from a very wide range of countries come to live and work in Scotland, it can be considered discriminatory to deny the right to vote to resident immigrants who are neither EU nor Commonwealth citizens”.
A Scottish Green source said the party would now look to amend the Referendums Bill when it came before Parliament to widen the franchise.
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Mr Harvie also said that while he "respected" the views of people who did not want a second referendum, they needed to "have the willingness to come forward with positive alternatives."
He added: "The status quo is broken and we should not ask Scotland to face the threat of a chaotic Brexit and a hard right Prime Minister, without the power to make our own choices about our own future.
“The UK Government has fundamentally attacked the devolution settlement people voted for over 20 years ago by legislating in devolved areas without the consent of the Scottish Parliament, and they are threatening to further undermine devolved powers with right wing free trade agreements which would endanger our environment, food standards and public services.
“We welcome the publication of the Referendums Bill today and look forward to scrutinising it in detail in the coming months. The Bill itself contains no specific commitment to an independence referendum during this parliament, but whether Brexit is eventually imposed on Scotland or not, we believe that such a referendum should take place on that timescale."