A veteran SNP MP warned restless independence supporters against holding a "dead end" declaration at Holyrood.
Pete Wishart said relying on a majority at the May election to achieve a split from the UK would be boycotted by Tories and lack legitimacy.
It follows a petition by a fringe movement called the Independence for Scotland Party.
On social media, Wishart warned: "Seen a petition going around for a 'plebiscite' from a pop up indy party that is polling less than 1%.
"Why would anyone sign up for a dead end that can't get us to indy, would be boycotted by the Tories, lack any democratic legitimacy & would appall the international community?"
Wishart, the MP for Perth and North Perthshire, said the party does not need "permission" from Tories, but added an agreed referendum would be "internationally recognised" and independence would happen "an awful lot faster".
Some independence supporters are frustrated that First Minister Nicola Sturgeon has not called a referendum without Westminster permission.
The call for a plan B has also been pushed by MP Angus MacNeil and councillor Chris McEleny.
In 2014, the UK Government temporarily devolved the power to hold a referendum and Sturgeon believes the same should happen in the event of indyref2.
Sturgeon's critics believe the plan is flawed and say Boris Johnson will continue to say no.
The PM again rejected calls for indyref2 at the weekend.
The Tory leader told the BBC's Andrew Marr programme: "Referendums in my experience, direct experience, in this country are not particularly jolly events. They don't have a notably unifying force in the national mood, they should be only once in a generation."
