Scotland First Minister John Swinney said there was “nothing that can be done” about postal votes that have not yet arrived for voters who are now overseas.
The SNP leader said he had “made it very clear about the fact some people will be disenfranchised” if their postal votes cannot be filled out and returned on time.
Mr Swinney said there had been “significant reports of people who were trying to vote by post who had applied properly for a postal vote before the deadline of June 19”.
Speaking to Sunday Morning With Trevor Phillips on Sky News, Mr Swinney said: “Unfortunately, there is nothing that can be done.
“They have to be here to be able to exercise their postal vote, if it’s been delivered to the house, or if there is an alternative arrangement in place.
“There are no other proxy arrangements that can be put in place, but I think it’s illustrative of the fact there was no thought given to summer school holidays.”
Local councils are responsible for sending postal ballot forms to voters.
Completed postal votes must have reached councils by 10pm on polling day, July 4.
They can be returned by post or handed in at council offices and can also be dropped at the correct polling station on election day.
Mr Swinney added: “I warned when the election was called that it was going to take place during the Scottish school summer holidays and many of our schools broke up for the summer last week.
“Those postal ballots have not arrived with people and some of them have now left the country, and they have been disenfranchised because of the timing of the election, which is something I deeply regret.
“I warned about the decision to have the election during the school holidays and welcome the fact that a number of local authorities in Scotland have taken emergency measures to establish centres which could enable people to exercise their postal vote.”
He said the SNP was a “unified and cohesive political party”, and the main concerns for voters were the cost-of-living crisis, cuts in public services and public spending.
Mr Swinney said the party had had “a bit of a tough time”, but added that voters “will get a substantial number of greater services that are provided by the Scottish Government that better meet their needs than other parts of the United Kingdom”.
He added: “I came into leadership of the SNP about seven weeks ago and became First Minister to essentially strengthen the party, to build a relationship with the electorate.”
