A senior SNP MP has criticised his party's support for a so-called People's Vote on Brexit.
Nicola Sturgeon has said her MPs would "undoubtedly" back a public vote on the final Brexit deal if it was an option.
But Pete Wishart warned that the move could create "all sorts of risks to a future independence referendum for nothing".
Mr Wishart is the SNP's longest-serving MP, and the chairman of the Scottish Affairs Committee at Westminster.
People's Vote campaigners have been pressing for a fresh referendum on whatever exit plans result from talks with EU leaders, with Ms Sturgeon confirming earlier this month that her party would back the move.
But Prime Minister Theresa May has already rejected the calls - and while Labour has not ruled it out, it wants a general election to decide the issue.
What did Mr Wishart say?
Writing in the National newspaper, Mr Wishart argued that backing a second referendum on Brexit would make it more difficult for the SNP to resist calls for a similar confirmatory ballot if Scotland was to vote for independence.
This would encourage "unreconciled unionists" to work "non-stop from the day after the referendum to ensure that a successful outcome would be overturned", he predicted.
The Perth and Perthshire North MP added: "Every apparatus of state would be deployed and they would ensure that the worst possible 'deal' would be offered to the Scottish people in the hope that their union could be rescued."
Scotland voted by 63% to 37% to remain the EU, while the UK as a whole voted by 52% to 48% to leave.
In Mr Wishart's article, he said he was "particularly anxious" about supporting a second Brexit vote "without any guarantees that our choice in Scotland will be respected next time round".
He wrote: "To say that we will sign up to a referendum without any guarantee that our Scottish national voice will be at least acknowledged is little more than an open invitation to have our national view ignored and disrespected all over again.
"We are simply inviting all the indignities we are currently enduring to be replicated and refreshed".
Mr Wishart stressed that he still hoped Brexit can somehow be stopped.
But he said that, with less than six months until the UK is due to leave the EU, this now seemed unlikely - and there is "just not the political capacity to win a second vote."
He concluded: "The few Tories likely to vote in favour will be swamped by the number of Labour MPs who believe that the "result must be respected" even if the Labour front bench could be tempted to support it.
"We could be presenting all sorts of risks to a future independence referendum for nothing".
Where does Nicola Sturgeon stand on a 'People's Vote'?
Ms Sturgeon, the SNP leader and Scottish first minister, told the BBC ahead of her party's recent autumn conference that her MPs would back a new Brexit referendum if it was an option.
She claimed the UK was heading for a "cobbled together" exit agreement that would be "almost as unacceptable as no deal at all".
And she predicted: "No doubt calls for a second referendum would grow in those circumstances, and I've said before we wouldn't stand in the way of a second referendum. I think SNP MPs would undoubtedly vote for that proposition."
Ms Sturgeon has also indicated she would seek a guarantee or "double lock" for such a ballot, for example requiring the support of all four UK nations before Britain could leave the EU.
SNP Westminster leader Ian Blackford has also suggested that the SNP could seek a guarantee that Scotland could hold another vote on independence in return for its support.
However it is unclear if the SNP would withdraw its support if its demands for special conditions are not met.
What has the reaction to Mr Wishart been?
Responding to Mr Wishart's article, an SNP spokesman said: "We have made it clear that we would push strongly for any second EU referendum to have safeguards to ensure Scotland's voice is protected in the event of Scotland voting remain again while the UK as a whole voted to leave."
Scottish Labour MP and People's Vote supporter Ian Murray said Mr Wishart's comments were proof that the "SNP's heart has never been in it".
He added: "Everything is seen through the prism of independence for the nationalists, putting party interest ahead of the country's interest.
"We are inching towards a parliamentary majority for a People's Vote, so this raises questions about how Pete Wishart and other SNP MPs will vote in the Commons."
And Lib Dem MSP Tavish Scott said SNP MPs should be backing the People's Vote campaign rather than "throwing up more roadblocks."