Scottish First Minister Nicola Sturgeon has said "sexist" portrayals of female politicians in the media - such as a mock-up of her in a tartan bikini - could deter women from entering politics.

Ms Sturgeon said it remains harder for women to succeed in politics than men, but said the elevation of several women to top positions in Holyrood represents "big progress".

She attacked The Sun newspaper's mock up of her as Miley Cyrus riding a wrecking-ball.

"That's sexist, there's no doubt about it," she told ITV breakfast television presenter Lorraine Kelly.

When asked if it was harder to be a women in politics, she said: "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 is tough.

"I think 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."

She added: "It does make me angry on behalf of younger women, because if a young woman who might think politics is something they are interested in, if they write something about me that is really derogatory, really personal, if that makes them less likely to want to come into politics then 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."

Holyrood's Presiding Officer, the leader of the Scottish Conservatives and Labour's most senior MSP are all women.

"That's big progress," Ms Sturgeon said.

"There is still a long way to go, and we need to keep moving that progress forward."

Ms Sturgeon predicted Labour will not rule out an alliance with the SNP after the general election, as the alternative would be to let "David Cameron waltz back into Number 10".

She also predicted Scotland will become and independent country one day following another referendum.

Ms Sturgeon later said that she believed "the time has come for quotas" of women in politics and beyond "because the pace of change, without that, is too slow".

Answering questions after a speech at the London School of Economics (LSE) she said: "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 I think it is time for us to give it a good kick up the backside and get it there."

She said there was a simple solution to resolving the gender imbalance of the House of Lords: abolishing it altogether.