Voters who have yet to receive their postal packs have been urged to “act today” to ensure their ballots count.

The Electoral Commission said it had been assured postal votes had all been sent out and Royal Mail has insisted there is no backlog.

It follows concerns raised by parties that some people may not receive their ballots in time to vote.

Voters have also been reminded to bring valid photo ID to their local polling station, which will be open from 07:00 and 22:00 on Thursday.

Andy O’Neill, head of the Electoral Commission Scotland, encouraged people not to wait until the last minute to act.

He told BBC Radio’s Good Morning Scotland programme: “If you have still got your postal vote the thing to do is fill it in as soon as possible and post it today.

“It has to be with the returning officer by ten o’clock tomorrow (22:00).

“If you fail to post it today you do have the option of taking it to a polling place tomorrow.”

As well as their own pack, an individual can take postal votes for up to five people to a polling station, where they will be asked to fill out a form.

Mr O’Neill said the commission had been assured that the postal votes were now all out.

Those who don’t have them can contact their council to obtain a new pack.

He said: “You can do that up to 5pm on polling day but I would urge people to act today, the day before polling, rather than leaving it too late.”

Photo ID was first required in Scotland for the Hamilton and Rutherglen West by-election last year.

But this is the first time it has been used in a national poll in Scotland.

The Electoral Commission says about 22 different forms of photo ID are acceptable, such as a passport, driving licence, bus pass and Young Scot card.

Mr O’Neill warned that for the local authority elections in England last May some voters arrived at polling stations with a photo of their passport.

He said: “It has to be an original document so don’t take a picture of it on your phone and try and show it.

“You will be turned away and you will have to go and get your original document.”

He also highlighted that out of date passports can be used.

But Mr O’Neill added: “The photo has to look like you.

“If your passport is ancient it possibly won’t work.”

East Lothian and Scottish Borders councils set up emergency facilities over the weekend to enable voters who will be away this week to collect postal packs in person.

Edinburgh, East Renfrewshire and Fife said they will keep their special facilities open until polling day.

The UK deadline to apply for postal vote applications was 19 June.

Any long-term postal voters or those who applied before 7 June should have received their voting pack last week.

But many people were unaware that if they applied after that date their voting papers would be sent out in a second batch, with some only dispatched in recent days.

In Scotland, where the school term ends earlier than elsewhere in the UK, some voters had left the country for summer holidays before their postal ballots arrived.

For those still in the country and without a voting pack, replacement packs can be obtained from council offices.

If voters are concerned about posting dates for returning them, many councils have arrangements for handing them in at offices.

Alternatively they can be handed in by voters in person on polling day at their local polling station.

But for anyone already out of the country there is little that can be done, barring a return home to vote.

The deadline for proxy votes has passed and emergency proxy votes are only possible in limited circumstances such as being called away suddenly for work.