He is credited with 'transforming' her into the national stateswoman she is

It depicts Sturgeon as a dominatrix in a short red dress with a whip in hand

It is a remarkable, eye-popping portrait of Scotland's First Minister, Nicola Sturgeon.

Entitled 'Naughty Nicola', the painting depicts her as a dominatrix in a short red dress, black suspenders on display and whip in hand.

But instead of being offended, Ms Sturgeon is 'tickled' by the image, so much so it is believed to grace the wall of her suburban Glasgow home after she was given it as a birthday gift by her husband, Peter Murrell.

He is the man credited with transforming the nationalist leader from surly apparatchik to national stateswoman – on the brink of holding the balance of power.

Eye-popping: The painting allegedly hanging in the home of SNP leader Nicola Sturgeon shows her as a dominatrix (pictured)

Couple: The image is said to grace the wall of Sturgeon's (left) suburban Glasgow home after she was given it as a birthday gift by her husband, Peter Murrell (right)

Softly spoken, bespectacled and almost unknown outside the Scottish political village, he can walk the busiest streets in Scotland without being recognised.

SNP colleagues reveal that within the party, Murrell is affectionately nicknamed Penfold, after Danger Mouse's loyal hamster sidekick in the 1980s cartoon series.

Meek, myopic and chubby, Penfold dutifully shouts 'Coming chief', whenever his superior summons him in the cartoons.

Some say the similarity extends further. Sturgeon doesn't drive and her husband frequently acts as chauffeur. He also carries out the lion's share of the domestic chores.

When Good Morning Britain's Susanna Reid remarked on the immaculate condition of the couple's detached house last month, Sturgeon, 44, said: 'That's because I had my husband up most of last night cleaning.'

Scotland's most powerful politician also leaves the cooking to her spouse, stating: 'I don't cook. I have had lots of disasters and now I prefer not to try, but Peter is a good cook and enjoys it.'

However, anyone assuming that Murrell's only role is that of dutiful house-husband would be sorely mistaken.

As chief executive of the SNP, he has transformed its fortunes, creating a formidable electoral machine.

Transition: Murrell (right) is the man credited with transforming the nationalist leader (left) from surly apparatchik to national stateswoman – on the brink of holding the balance of power

Portrait: Instead of being offended, Ms Sturgeon (pictured) is 'tickled' by the image depicting her as a dominatrix

In 2001, when he took on the role, the party had a paltry 6,000 members; today the SNP is the third-biggest party in the UK, with a membership of 110,000.

Murrell, who earns about £120,000 a year, and his wife first met when Ms Sturgeon – an 18-year-old firebrand Left-winger – attended an SNP gathering which he helped to organise.

They were married in 2010 with a wedding cake created by the Scottish confectionery dynasty Tunnock's.

So was Glasgow-based French artist Laetitia Guilbaud making her own comment on the Sturgeon-Murrell relationship when she dreamt up Naughty Nicola in 2009?

'No, not at all,' Ms Guilbaud, 35 told The Mail on Sunday. 'At the time she was very prominent, but I knew nothing about her partner.

'Her image was quite mousey and she often wore a red suit, so I just wanted to explore her sexy side.'

Mr Murrell certainly liked what he saw and snapped up the work for £1,500. He said: 'Nicola was tickled by the depiction.'