Stewart Hosie, a senior member of the Scottish National Party, said the UK parliament could have a vote of confidence in the government next week.
The SNP MP told BBC Radio 4 Today Today that an untrustworthy vote could be the only option to stop a Brexit without agreement on October 31, which British Prime Minister Boris Johnson has repeatedly said he would like to do.
"We have to do this because there is now no confidence that the prime minister will comply with the law and seek the extension that parliament voted only a few weeks ago," Hosie told the BBC.
"If we take extension seriously, this is the only game in town."
The former SNP deputy leader added that all opposition parties, as well as conservative rebels, would need to unite to prevent a Brexit without agreement.
This comes after the Telegraph newspaper reported that the SNP and the main opposition labor party were discussing the possibility of voting together.
SNP leader Nicola Sturgeon seems to recently support the idea of labor leader Jeremy Corbyn taking control if the Boris Johnson government collapses.
But the other major opposition party, the Liberal Democrats, says Corbyn is too divisive to become prime minister.
If any new government could not get the support of the majority of parliamentarians, an election would be held.
If Johnson is toppled next week, he will be the lowest ever prime minister in the UK, lasting only two months.