Talks between the First Minister, unions and local authority bosses over pay disputes have been “constructive” despite ending without a deal, a trade union has said.

Johanna Baxter, head of local government for Unison Scotland, said it is now down to local government body Cosla to determine whether to revise the pay offer at the centre of a row which has seen mountains of rubbish pile up in towns and cities across the country.

Discussions with Cosla leaders resumed on Friday morning after Thursday’s meeting ran late into the evening.

Ms Baxter told BBC Radio Scotland’s Good Morning Scotland programme that things are more optimistic than they were 24 hours prior, and there is a “willingness from all sides to make movement”.

She added: “I think the judgment for Cosla leaders this morning is whether they have enough to deliver what we need for our members.”

She said the marathon talks on Thursday, which were chaired by Nicola Sturgeon, looked into how much money is on the table and how it is constructed.

“Unison’s position has always been that if we had been talking about a flat rate – the like of which was in the pay claim, so £3,000 for everybody – then we wouldn’t have had any debate about the flat rate.

“The difficulty obviously has been the money, and how much money has been on the table.

“The difficulty we face particularly in the last week is the fact that however you cut the 5% that was on the table in terms of consolidated money, and that is recurring, then you couldn’t get a flat rate that worked for the majority.”

Further strikes by waste workers are planned for next week, with staff at a number of local authorities expected to walk out for eight days.

Workers in schools and early years learning will also take part in a three-day strike in some areas.

Leaders from Cosla began a meeting at 9am on Friday to discuss a revised offer to be put to the unions.

When the unions receive the new offer, committees of their representatives will discuss whether to accept it or not.

Strikes due to go ahead next week could be suspended if the offer is accepted.

A spokesman for GMB Scotland said: “We believe progress has been made and would hope last night’s negotiations will result in a fresh offer that can be put to our local government committee for review.”