Inverclyde Council announces Cosla departure
Another council - Inverclyde - has confirmed it plans to leave the body representing Scottish local government.
Three other councils have already warned they may go. At least two more are expected to consider leaving shortly.
At the root of the rupture in Cosla is a row over the way government cash is allocated to councils.
This has brought simmering tensions about power within the organisation to the boil.
The Inverclyde decision was made as part of the council's budget announcement.
The council will give the Edinburgh-based organisation which represents Scottish councils notice to terminate membership from 1 April, 2015.
Council leader Stephen McCabe said: "The constitutional review which was approved by Cosla is due to report in June 2014.
"If this results in a significant transfer of power from the leader's group to the convention, this would seriously reduce the influence of this council and lead us to question the value to Inverclyde of our continuing membership of Cosla.
"Therefore we are giving Cosla the statutory notice of our intention to leave the organisation."
But Mr McCabe said the council had left the door open to withdraw its notice to quit.
He added: "Depending on the outcome of the Cosla review, we reserve the right to withdraw our notice to terminate our membership."
Because of the way power lies at Cosla - which currently represents the collective interests of all 32 councils - it can be difficult to reach agreement on controversial party political matters.
Some Labour councils want to see Cosla take a more proactive stance against government policies which they believe are harming their interest.
Labour leads 16 Scottish councils but the way power lies at Cosla is much more subtly divided.
Inverclyde claims possible changes to Cosla's internal structure could weaken their influence within the organisation.
Aberdeen and Renfrewshire have already indicated they will quit.
South Lanarkshire and Glasgow councils are both expected to take a decision on whether they should also leave Cosla soon.
Separately, Dumfries and Galloway Council is also to consider leaving the organisation.
Councils need to give a year's notice so any councils which leave will do so in April next year.
Leaving Cosla will make no difference to local services or the level of the council tax.
However, some are concerned it could lead, in time, to the end of national agreements on pay and conditions for council staff.
There have also been warnings that if Cosla is weakened, it could undermine the power of councils across Scotland.
Some claim there has been a process of creeping centralisation in Scotland since devolution and that an organisation representing all the country's councils can act as a barrier to this.