Waste service and school workers have said First Minister John Swinney’s constituency will be their “first target” for strikes after union members rejected a pay offer from Scotland’s national councils association.​Unison council workers in Perth and Kinross said they are angry that a recent pay offer from the Convention of Scottish Local Authorities (Cosla) was not in line with other public service workers in the area, some of whom they say have been offered 5.5% pay rises.

They have been offered a 3.6% increase.

The union has strike mandates in 13 local authorities, including Perth and Kinross.

It is now considering on which dates staff will take industrial action.

It comes after thousands of school and early-years workers rejected the pay offer, with 92% stating they were in favour of striking.

Earlier on Friday, GMB accepted the 3.6% increase and Unite the Union is still to announce its decision.

Unison Scotland said it hopes that by focusing on Mr Swinney’s constituency, he will take action.

Unison Scotland local government committee chairwoman Colette Hunter said: “Focusing on the First Minister’s constituency will bring home to him the importance of settling this dispute as schools close and rubbish piles up in the streets.

“Local government staff are angry that after years of pay cuts, they’re not getting a pay rise comparable to other public service workers.

“They’re expected to deliver even more with fewer staff and lower wages, but that puts workers under intolerable pressure.

“It’s unsustainable and can’t go on.”

Unison Scotland local government lead David O’Connor said: “Going on strike is never an easy decision, as council staff are acutely aware of the disruption it causes.

“They’re asking why they have to do this every year.

“There’s a high bar to reach the legal threshold imposed by union laws, so not all councils achieve the mandate required.

“However, the anger is palpable. Thousands have rejected Cosla’s pay offer, with an overwhelming majority (92%) of those who voted agreeing to strike.

“The First Minister’s constituency will be the initial target, ensuring he cannot overlook the real anger among staff regarding this inadequate pay offer.”

A Scottish Government spokesperson said: “While the Scottish Government respects workers’ rights, nobody’s interests are served by disruptive industrial action which harms our communities and economy.

“GMB Scotland members have already voted in favour of a fair, above-inflation pay deal for local government staff, which allows this hugely valued workforce to continue serving communities.

“Most workers will see an increase of more than 4.0% and the lowest paid will receive an increase of 5.63%.

“Ministers encourage all those involved to continue to work towards a resolution and avoid industrial action.”

Cosla was contacted for comment.