Neale Hanvey who represents Kirkcaldy and Cowdenbeath in the Commons, announced over the weekend he would stand on the Mid Scotland and Fife regional list in the Holyrood elections for the Alba Party.
The new party has seen a number of defections from the SNP, including East Lothian MP Kenny MacAskill, and most recently former SNP MP George Kerevan and SNP Common Weal Group founder Craig Berry.
The party’s equalities and women’s conveners, councillors Lynne Anderson and Caroline McAllister, have also quit to join Alba.
Speaking on the BBC’s Good Morning Scotland, Mr Hanvey was challenged about potentially holding a “dual mandate” in both parliaments, but said he believed that would benefit his constituents.
"I think that's a very real advantage for my constituents,” he said.
"It means that they effectively have a one-stop shop for both parliaments and that would enable me to act in their interests in both parliaments simultaneously.”
The SNP has attacked Scottish Tory leader Douglas Ross over his intentions to sit in both Holyrood and Westminster if he is elected to the Highlands and Islands region.
Mr MacAskill has said he will not stand to retain his seat at Westminster at the next general election. However, Mr Hanvey would not be drawn on making the same commitment.
"It is my intention that we have no further need to stand for any seats in Westminster," he said.
"I'm not a career politician, I'm doing this to achieve independence for Scotland. That is my absolute ambition, so I'm going to keep focused on that rather than talk about my career ambitions for another term in either the Scottish Parliament or the Westminster Parliament."
Mr Hanvey was recently sacked from his frontbench role in the SNP Westminster group by its leader Ian Blackford.
He had also previously been suspended by the party during the 2019 general election campaign while it investigated allegations he had tweeted anti-Semitic statements. He was later able to re-join the SNP group.
When asked if more of his former colleagues were set to defect, Mr Hanvey said: "I really don't know.
"They would be more than welcome. I don't see there being a tremendous amount of conflict between being in the SNP at Westminster and the Alba Party at Westminster.
"We have very little, unfortunately and quite starkly, influence over policy from Westminster, even when it's being forced on the people of Scotland, even against the majority vote of Scottish MPs.
"I'm much more focused on how I can utilise my position in Westminster in concert with a position in Holyrood, to maximise the impact on behalf of the people of Scotland to secure our independent future."
Following Mr MacAskill's decision to leave the party, Mr Blackford described the move as a "relief", adding: "He has been an increasing embarrassment to many in the SNP."
Mr Hanvey said Mr Blackford should "reflect" on his comments.
"If they want to be ungracious, I don't really want to comment on that or give it any further fuel," he said.