UKIP Scotland's sole MEP has slapped down one of his advisers for making a "stupid" sick joke about celebrated physicist Stephen Hawking's motor neurone disease.

Robert Malyn, who works for David Coburn MEP, mocked the idea of former Prime Minister John Major leading the UK team for a renegotiated deal with the European Union.

"Its about as convincing as appointing Stephen Hawking as captain of the British Synchronised Swimming Team!" he wrote on social media.

A spokeswoman for Motor Neurone Disease Scotland (MND) said the comments would be "hugely upsetting" to sufferers.

Coburn became the anti-EU party's first elected representative in Scotland following a fractious European election campaign last year.

He is able to draw on a €254,508 a year staffing allowance and has used it to employ a number of party allies.

According to social media site Linkedin, Malyn used to work at a water treatment plant and as a "helpdesk analyst" for internet provider Thus.

In September, he was employed by Coburn and describes himself as a "political advisor".

His comments about Hawking, whose neurological disease left him almost entirely paralysed, were made in December, three months after he started the job.

Coburn said: "It's a pretty stupid thing to say and I'll have words with him. People say daft things and they think that it's clever, but it's not clever and it's not funny."

He said the acclaimed film about Hawking's life, The Theory of Everything, had made him "blub".

Malyn is one of six employees listed on Coburn's register of interest.

His chief of staff, Misty Thackeray, has also attracted criticism for his Facebook posts.

He once wrote of the council in Glasgow: "No wonder the blue half of my city say G.C.C actually stands for the Glasgow Celtic Council for Gays Catholics Communists"

In 2011, he posted: "You have to witness a Glasgow election count night to understand the extent of islamist influence within the SNP and Labour ... last time out I thought we were contesting a seat in"

Matthew Grainger, UKIP's Glasgow chair and an advertising student in the city, is the MEP's press officer, while party candidate Oluf Marshall is also listed as a staffer.

Regional organiser Kevin Newton and heating and gas engineer Robert Sale are also declared as staff.

UKIP announced plans last month to field candidates in at least 40 of the 59 Westminster constituencies in Scotland.

The party also launched its general election campaign in Glasgow recently and Coburn said he was confident UKIP could win seats north of the border.

Susan Webster, Head of Policy and Campaigns at MND Scotland, said: "The comments will be hugely upsetting to 400 people in Scotland living with the enormous burden of Motor Neurone Disease. The likes of Stephen Hawking, Gordon Aikman and Fernando Ricksen have demonstrated a huge amount of courage recently in helping us to combat ignorance over the disease and create a far more sensible, informed discussion."

Scottish Conservative chief whip John Lamont said: "Mr Coburn's earned a reputation as a mouthpiece who'll basically say anything in the hope it upsets someone. Now we know where he's been getting this ill-judged advice from."

SNP MP Angus MacNeil said: "These comments are clearly in very poor taste - but they demonstrate exactly why UKIP and their nasty, divisive politics are getting nowhere in Scotland."

Malyn said: "I 100% stand by the sentiment that Sir John Major is totally unsuitable to lead British negotiations with the EU, given Mr Major's enthusiasm for the EU super state project and the way he pushed through the Maastricht treaty. However I do certainly regret using that particular analogy. It was clearly wrong and I apologise for any offence given."