A controversial EU-US trade deal could have a detrimental impact on Scotland's economy, threatening jobs and undermining attempts to reduce inequality, MSPs have been told.

The Transatlantic Trade and Investment Partnership (TTIP) aims to remove barriers between the European Union and the US, making it easier to buy and sell goods and services and open up markets.

Critics have warned that the deal, which is still being negotiated behind closed doors, offers few gains for the Scottish economy and poses a threat to public services.

They are particularly fearful about the impact of the investor-state dispute settlements (ISDS) part of the deal, which could allow companies to sue governments for acting in a way that jeopardises their ability to make profits.

Giving evidence to Holyrood's European and External Relations Committee, Stephen Boyd, assistant secretary, of the Scottish Trades Union Congress, told members that the organisation is "very, very sceptical about the economic benefits of TTIP".

He said barriers between the EU and the US are already low and therefore any gains from TTIP are likely to be "minimal at best".

"We are very concerned that TTIP will lead to a general lowering of standards across the economy of a whole and will be actively detrimental to the economic-social model that I think the Scottish Government is trying to create in Scotland," he said.

"We need to be clear that (TTIP) is not about removing what we would traditionally describe as barriers to trade, it is about imposing a common regulatory structure that will be policed by an international mechanism that would not be passed by the normal democratic processes in each country. I think that is really crucial to understand."

He added: "Even some of the models that have been used to promote the economic benefits have actually been quite clear in saying there will be job losses as a result of this.

"People who are displaced are very unlikely, evidence shows, to gain jobs that pay similar rates or employ them at a similar level of skill.

"Although you might be able to argue that the economy as a whole will benefit in the future, there will be big distributional impacts and if we are always concerned about inequality, as we all proclaim to be at this moment in time, then we need to understand that trade agreements have a major, major impact on that moving forward."

The UK Government says TTIP will create jobs and growth by reducing tariffs, harmonising regulations and making it easier for Britain to trade with the US.

Many critics of the deal have warned that the ISDS section could lead to US corporations attempting to sue the UK or Scottish governments if they are excluded from public-sector areas such as the NHS.

Dave Watson, Scottish organiser (bargaining and campaigns) at Unison Scotland, said that there has been no "unequivocal exclusion in the area of public services".

He said: "Big US corporations have a big footfall in the health service in the United States and will see this as an opportunity to come in and privatise large chunks of the NHS."