Scottish Government plans to freeze council tax have been branded “electioneering at its worst”.

First Minister Humza Yousaf announced the move on Tuesday in his first speech to the SNP conference as leader, scrapping plans featured in a consultation that would see rates increased by between 7.5% and 22.5% on the highest band properties.

But within minutes of Mr Yousaf’s announcement, concerns were raised about funding for local authorities, which have been struggling to provide services in recent years, including by local authority body Cosla, which said it had not been told of the announcement before it was made.

Speaking to BBC Radio Scotland on Wednesday, Dave Moxham, the deputy general secretary of the STUC, said: “What the First Minister didn’t say is that we pay on average about £500 less per person up north than they do down south.

“This is something the Scottish Government has developed over a decade, and the effect of that has been an incredible squeeze on local government services, and that has to stop.

“This announcement doesn’t help, but it’s electioneering at its worst.”

Mr Moxham also said the STUC, which had representatives at the conference, had no idea the announcement was going to be made.

“It was something of a surprise to find that £100 million has just been discovered in the cupboard that wasn’t there a few days ago,” he said.

“I’m afraid to be slightly cynical and say it’s party conference season and that’s really what’s brought it about.

“But it really is a bad policy at a bad time.”

It is not clear how much the policy will cost the Scottish Government.

Within minutes of the announcement, the Scottish Greens – the SNP’s governmental partners – voiced concerns about the policy, with finance spokesman Ross Greer saying they were “concerned about the effect this freeze could have on already-strained frontline public services if it is not properly funded”.

A spokesperson for Cosla said: “We have just heard the announcement made at the SNP conference in relation to freezing council tax. We were unaware of it in advance.

“This has longer term implications for all councils right across the country, at a time when we know there are acute financial pressures, and where we are jointly looking at all local revenue raising options.”