The election watchdog has opened a probe into the Scottish Liberal Democrats' spending during the last Holyrood election.

The Electoral Commission confirmed it received a complaint regarding the party and will now investigate if its returns from the 2016 election were "true and accurate".

It is understood the probe will consider if spending was correctly attributed between individual candidates and the party's national spending.

The Lib Dems said spending was "apportioned correctly" and it has "full confidence that there is no substance to this complaint".

A spokeswoman for the watchdog said "The Electoral Commission has opened an investigation into the Liberal Democrat Party's spending return at the 2016 Scottish Parliament election."

Parties could spend a maximum of £12,000 in trying to win each constituency election and a further £80,000 across the regional list vote.

The Lib Dems spent a total £186,477 during the election, with more than three-quarters of the funds going to unsolicited materials to prospective voters.

The opening of the probe comes four months after prosecutors announced no action was being taken against Lib Dem MSP Alex Cole-Hamilton after Police Scotland conducted an investigation into his campaign spending.

The Crown Office and Procurator Fiscal Service (COPFS) concluded that no proceedings should be taken at this time following a "full and careful" look at the case.

Cole-Hamilton stood as a candidate in both the Edinburgh Western constituency and on the party list for the Lothians region at the election.

The Commission said it waited until the outcome of police probe "before considering whether to open an investigation into party spending".

Separately, Police Scotland are considering a complaint regarding the electoral return of Lib Dem MP Jo Swinson from last year's general election.

A spokesman for the Scottish Liberal Democrats said: "This is a classic SNP tactic when they have lost an election. Last year they wasted 13 months of police time with their complaint about the election in Edinburgh Western, and the police found there was no case to answer.

"All expenditure in this election was apportioned correctly and clearly identified in our election return which is a matter of public record. We have full confidence that there is no substance to this complaint.

"Perhaps the SNP should spend less time whinging when they lose an election and more time addressing the problems they have created for themselves in education, health and the police service. It's no wonder that their government are on the slide."

A spokesman for the SNP said: "The widespread suspicion is the Lib Dems wrongly declare constituency expenses as party expenses to disguise exceeding local spending limits."

He added: "Something stinks about the way the Lib Dems go about election spending. With thousands of pounds of fines under their belt, it's about time they cleaned up their act."