NICOLA Sturgeon has warned "sexist" portrayals of female politicians in the media, such as the mock-up of her in a tartan bikini, could deter women from entering politics.

The First Minister insisted it was still the case that it was harder for women to succeed in politics than men but said the elevation of several women to top positions at Holyrood represented "big progress".

She attacked The Sun's mock-up of her as Miley Cyrus riding a wrecking-ball, saying: "That's sexist; there's no doubt about it."

The newspaper is currently serialising The Dream Shall Never Die, the independence referendum diary of her colleague, Alex Salmond.

Ms Sturgeon told ITV breakfast television presenter Lorraine Kelly, when asked if it was harder to be a women in politics: "It is to some extent. Some of things that are said about women in politics, the way you are characterised, the way you are described, the focus on how you look and what you wear; it is tough."

But she noted: "It is changing for the better and the more women we have in senior positions in politics the more that will change and the faster it will change."

The SNP leader admitted that it angered her if something derogatory or personal was written about her because of her gender, which might put off young women from entering politics as a result.

"That is a real shame. I don't want to sound too pious about this but, if I can help change that for the women coming after me, then I am really keen to do that."

Ms Sturgeon said the fact that Holyrood's Presiding Officer, the leader of the Scottish Conservatives and Labour's most senior MSP were all women was "big progress" saying: "There is still a long way to go and we need to keep moving that progress forward."

Later, in a question and answer session following a speech at the London School of Economics, the FM said she believed "the time has come for quotas" of women in politics and beyond "because the pace of change, without that, is too slow".

She told the audience of mainly students: "We don't have a meritocracy right now because it we did we'd have gender balance. The pace towards that has been painfully slow and it is time for us to give it a good kick up the backside and get it there."