A trade association which represents bus companies has said there are serious questions over the Scottish government's plans to bring the bus network under public control.

Paul White, director of the Confederation of Passenger Transport (CPT) in Scotland, said the first minister announced "a policy statement but no detail behind it".

"We need to know what is meant by public control and how it will impact existing legislation and bus partnerships across the country before we can form a view," he added.

First Minister John Swinney said the Scottish government would work with parliamentary partners and bus companies to deliver a bus network that operated in the public interest.

At the SNP conference in Aberdeen on Saturday, John Swinney announced during his keynote speech that the bus network would be brought under public control by 2031 through franchising and regulation, with a bill to be tabled in Holyrood next year.

It has been suggested the changes will allow regional transport partnerships to have more control over route and fares on the bus network, without the government having to actively own it.

Through franchising, it is understood, the government will outline plans for routes and timetables, then ask the bus operators to compete for the business.

The successful companies for each route will be paid to operate the service and the government will receive the fare revenue.

"With a franchise, you are replacing competition within the market for competition for the market," White told BBC Radio Scotland Breakfast.

He said this model could be used to regulate buses but raised questions over how it would be funded and what impact it would have on small and medium-sized enterprises (SME).

"We have about 150 bus operators in Scotland and a number of our members are concerned about what it will mean for their operation if they are not successful in their bids to run the service," White said.

Under the proposals, there have been claims from bus operators that they could go "out of business" if they do not win the contracts.

White suggested this was the reason why operators, such as McGill's, had spoken out about their concerns and wanted to understand what it would mean for their business.

"There are examples in England where it has been difficult within these franchises to carve out a role for the many SMEs that exist in the bus sector," he added.

"Our concern is about finding out more detail at this stage and we need to appreciate there are a number of businesses out there that really need to know what will happen to them after 2031.

"We are very alive to the potential implications, which is why we need to sit down with the first minister."

Pierce Glennie, co-founder of electric bus company Ember, described furious reaction from the owners of McGill's - the UK's largest independent operator - as "absurd".

Sandy Easdale, who owns McGill's alongside his brother James, accused the first minister of behaving like a dictator and threatened legal action to block the plan.

Glennie said Ember, which primarily operates intercity routes, was a "good example of what competition can allow", but also raised concerns about the lack of detail in Swinney's statement.

"At worst, the regulation would mean we are not able to carry passengers for short journeys, which would be a concern because most of these are from rural village to rural village," Glennie said.

"I hope that is not how it is implemented and the government is sensible about this."

He claimed taking the bus network into public control would not directly solve the issue of rural routes, as councils already had funding available to support these.

Glennie added that he wanted "substantive discussions, not announcements."

The first minister said a model of regulation and franchising would help "significantly strengthen the availability of services around the country".

He told BBC Scotland News: "I'm interested in substantial and engaged discussion about turning these aspirations into a practical reality".

But Swinney warned against "hysterical language", describing Easdale's comments as "completely over-the-top, to be blunt".

"I think we've all got to be pretty careful about the language that we use, and some of the language that we have used is just frankly laughable," he added.

At the SNP conference, Swinney also announced the extension of the £2 bus fare cap, with Aberdeen and Aberdeenshire to be covered from April.

The current cap covers Glasgow and the west of Scotland as well as the Highlands and Islands, with the government planning to expand it to the whole country by the end of the parliamentary term in 2031.

Dr Nick McKerrell, a senior lecturer in law at Glasgow Caledonian University, made comparisons between the first minister's announcement and Prime Minister Andy Burnham's decision to introduce a franchised network in Manchester.

"There was not a lot of detail in the speech other than phrases around the public control of bus services, which is similar to the rhetoric that the prime minister has said," he told the programme.

McKerrell added that a franchise model would be "complex" to develop.

Since the 1980s, when Margaret Thatcher deregulated the network, most bus routes in the UK have been run by private companies. They decide routes, fares and timetables.

Critics say this has led to popular, profitable routes being over-served by multiple operators, while quieter areas lose out.

To combat this, buses in London, Manchester and Liverpool have been brought under public control.

Under these franchise systems, private firms are given contracts by a local authority to put on buses.

According to a report published by Transport for Greater Manchester last year, there had been a 14% year-on-year increase in bus journeys and improved punctuality in areas where buses had been taken under public control.

Scotland's local authorities have the power to create their own bus franchises, but doing so is not straightforward.

In Greater Manchester, for instance, then mayor Andy Burnham faced legal challenges to his plans.

The Strathclyde Partnership for Transport (SPT), which runs the Glasgow Subway and bus stations in and around the city, has published an action plan that proposes returning bus services to public control.

However, SPT anticipated that it would take several years to get the scheme up and running.