Scottish Government estimates that 336,000 jobs are directly associated with European Union (EU) exports have been challenged by independent parliament researchers who say the actual figure is just a quarter of this.

Just 81,000 jobs are directly associated with EU exports, according to the apolitical Scottish Parliament Research Centre (Spice).

Even if indirect jobs are included, such as supply-chain work and spending by employees, the total direct and indirect jobs associated with EU exports is less than half the SNP administration's estimate at only 150,000.

The Scottish Government opposes an EU exit, demanding a veto to prevent Scotland being dragged out against its citizens' will and suggesting such an outcome would be a precursor to another independence referendum.

Spice has produced a research paper to inform the debate over the proposed in/out referendum on EU membership.

It states: "In March 2015, the Scottish Government published a report (which) states that 336,000 Scottish jobs are estimated to be directly associated with exports to the EU, excluding the UK.

"The financial scrutiny unit in Spice has calculated the number of jobs sustained directly by Scottish exports to the EU (and estimated) that around 81,000 jobs were sustained directly in Scotland from exports to the EU in 2013.

"Multiplier effects take into account additional jobs beyond those created directly by exporters (including) jobs supported by the supply chain of exporters and additional spending by employees.

"As a result of including these multiplier effects, the number of direct and indirect jobs sustained by EU exports in Scotland is around 150,000 full-time equivalent jobs."

The UK and Scottish governments both want EU reform but disagree over the scope and tactics.

The SNP wants "a more democratic, effective and efficient" EU and the Tories want to cut red tape and block unwanted EU legislation.

They are at odds over social policy, with the Scottish Government calling for developments in workers' rights and freedom of movement.

The UK Government wants to limit the application of the Working Time Directive, which restricts the length of time employees can be made to work, and introduce new controls to stop "vast migrations" when new countries join the EU and limits to stop EU citizens cashing in on "free benefits".

Spice confirms that Scotland is a net contributor to the EU, providing £5,585 million to the EU budget and getting £4,739 million in receipts.

Since 2002, EU exports as a share of all international exports have followed a downward trend, with exports to North America growing nearly five times as quickly as exports to the EU, but the EU is still by far Scotland and the UK's biggest market.

Nearly seven times as many EU students come to study in Scotland than Scottish students who go to study in other EU countries.

Some 13,550 EU students benefited from tuition fee-free Scottish education in 2013/14, costing the Scottish Government £25.6 million, but only around 2,000 Scottish students studied in other EU countries.

Scottish organisations have received about £80 million in funding from Europe's Horizon 2020 research and development programme since January 2014.

Spice said it has not analysed the impact, positive or negative, of a UK decision to leave the EU because "it would be very difficult to quantify what might happen in the event of a withdrawal given the current lack of clarity about any alternative to EU membership".

It cites expert evidence warning of a "constitutional crisis" if the UK votes to leave.

Professor Sionaidh Douglas-Scott, from Oxford University, has suggested Holyrood may refuse to implement UK efforts to unpick EU law from Scottish legislation.

"Although the UK Parliament may amend the devolution Acts, the UK Government has stated that it will not normally legislate on a devolved matter without the consent of the devolved legislature," she said.

"The devolved legislatures might be reluctant to grant assent ... so the need to amend devolution legislation renders a UK EU exit constitutionally highly problematic."