Planned bin strikes in Aberdeen and Aberdeenshire and other Scottish local authorities are to go ahead after unions queried a new pay offer.
Rubbish has already been piling up in Edinburgh where hundreds of GMB and Unite union members in the city's waste and recycling service have walked out.
The first Aberdeen strike is due to start tomorrow and action in Aberdeenshire begins on Friday.
Local authorities have increased their pay offer from 3.5% to 5%, but Unite said it would not put the offer to its members due to "insignificant detail" about how it affects lowest-paid workers.
The BBC says the strike in Edinburgh is the first in a series planned across Scotland.
Further walk outs by workers in waste and recycling services is planned in the following councils:
Unite - August 24 to 31:
Aberdeen, Angus, Clackmannanshire, Dundee, East Ayrshire, East Lothian, East Renfrewshire, Edinburgh, Falkirk, Glasgow, Highland, Inverclyde, South Ayrshire, South Lanarkshire and West Lothian.
Unison - August 26 to 29 and September 7 to 10:
Aberdeenshire, Clackmannanshire, East Renfrewshire, Glasgow, Inverclyde, North Lanarkshire, Stirling and South Lanarkshire
GMB - August 26 to 29 and September 7 to 10:
Aberdeen, Angus, Dundee, East Ayrshire, East Lothian, Falkirk, Glasgow, Inverclyde, Highland, Midlothian, Orkney, South Ayrshire, South Lanarkshire, West Lothian, Perth and Kinross, and North Lanarkshire.
On Monday, following a meeting of Unite's local government representatives committee, the union said it would not take the new 5% offer to members.
Alison Maclean, Unite industrial officer, said: "Unite's local-government committee has reaffirmed that the strike action ongoing in Edinburgh and scheduled to take place in a further 14 councils continues as planned.
"There remains insignificant detail on the 5% pay offer, and what this in reality means for the lowest-paid workers.
"At this moment, the offer from Cosla remains a vague aspirational pledge but Unite can't take anything to our wider membership unless we have specifics and guarantees."
Unite and GMB Scotland are to meet with Cosla today - after which Unite said it would "reassess the situation".
GMB Scotland senior organiser Keir Greenaway said members wanted clarity from Cosla about whether the 5% proposal came with the assurance of a flat-rate award - a key demand of the union pay claim.
He added: "The prospect of the highest paid getting the biggest cash increases in any offer would be unacceptable, let alone one that is still well below inflation."
UK Ministers preparing for possible general strike
It also emerged today that UK Ministers are preparing contingency plans for a cross-government strike by public-sector unions which could be announced during next month's Labour party conference.
Officials in the Home Office and the Cabinet Office are drawing up detailed plans about how to cope with strike action over pay which they expect to be announced on September 26, during the conference in Liverpool.
Ministers are expecting other public-sector unions to follow suit, which could mean large parts of the Civil Service are shut down in the months leading up to and after Christmas.
The Telegraph says different public sector unions are likely to strike on different days in a series of rolling stoppages to maximise the disruption.
There is speculation that the scale of the unrest could approach that of the general strike from 1926 when millions of workers walked out for nine days.