Marathon talks between Nicola Sturgeon, unions and local authority bosses has ended without a deal.

The First Minister met with leaders from the three unions involved in the local government pay dispute which has seen mountains of rubbish pile up in towns and cities north of the border.

Late on Thursday, a Scottish Government spokesman said “detailed negotiations” had taken place and had “carried on late into the night”.

Discussions had started at its Edinburgh headquarters at 2.30pm, and had even seen pizza delivered as talks progressed into the evening but, at about 10.40pm, the government urged sides to reach a settlement.

“We are grateful to all parties and would encourage all sides to continue to seek a fair and sustainable settlement,” the spokesman said.

The discussions came after clean-up work got underway in some of Scotland’s largest councils after several days of action by cleaning department workers.

Rubbish piled up on the streets as a result of the action – and Wendy Dunsmore of Unite warned that without a deal the unions will seek to step up the pressure.

Fresh strikes by waste workers are already planned for next week, when staff at a number of local authorities will walk out for eight days, while the dispute will also spread to schools and early years workers, who will take part in a three-day protest in some areas.

Unite is calling for a flat-rate increase of £3,000 for all council workers, although in a video posted on social media, Johanna Baxter of Unison – the largest of the three unions involved in the dispute – appeared dismissive of such a deal.

For such an offer to  be acceptable, Ms Baxter, the head of local government at Unison Scotland, said there would need to be more money on the table, saying without it, a deal risked “literally taking money out of the pockets” of some workers.

Unite – which is involved in the dispute alongside Unison and the GMB – said earlier that it has served notice of strike action in 20 local authority areas.

However, Ms Sturgeon has already warned that all options for making more funding available for pay have been “exhausted”.

The First Minister tweeted: “If we could go further we would, but @scotgov budget is finite.”

Ms Dunsmore told BBC Radio Scotland she will use the meeting to demand a “fair and decent pay rise for all workers”.

The Unite regional officer told the Mornings With Stephen Jardine programme: “We’re hoping she is intervening to get a resolution to this crisis we are in.

“Our members don’t want to be on strike any more than anyone else would want our members to be on strike, but that is the position they have been forced to take.”

Unions have already rejected a 5% pay rise offered by local government body Cosla, with Ms Dunsmore insisting the current offer shows “disregard for the lowest paid”.

She continued: “What we want is a fair and decent pay rise.

“Our claim is £3,000 flat rate. Right now, they are offering £2,000 to the highest-paid workers, but for others they are offering far less but with a cash incentive or a cash payment.

“The cash payment will disappear quite quickly with tax and insurance. If I was Cosla or the Scottish Government, I would definitely look at consolidating that into pay because then it would be worth something today, tomorrow and in the future.”

She made the plea as clean-up operations got under way in parts of Scotland, including Glasgow, the country’s largest local authority.

However, Glasgow City Council told residents to expect a “significant delay to all collections” due to the “extensive backlog”.

Aberdeen City Council also said there is a large backlog of work and warned “there may still be disruption to normal services”.

According to the Scottish Government, the latest offer included a payment of at least £1,925 for council staff, with those earning £20,000 receiving £2,000.

But Unite said the payment could be as low as £989 for some employees, with 85% receiving between £1,925 and £2,000, and any payment would not be recurring.

If no deal can be reached, Ms Dunsmore said unions – who have already warned of a possible winter of discontent – could escalate their action.

“The industrial action next week is three days in schools and early years, and in waste is eight days,” she said.

“What happens after that is the unions will regroup and will look to escalate this further, so that could have further impacts on services across Scotland.”

She added: “Our members are very resolute on what they’re looking for. They cannot afford to work in poverty. so we’re having to make plans and a strategy as to meet the needs of our members.”