A new report has highlighted the gender inequality of the the art world.

The online art sales site Artfinder, in a bid to stoke a wider debate on the issue, has drawn attention to the lack of female representation in the "high end art world."

Artfinder is now to write to every major art institution in the UK and the US asking them to share their data on the representation of women artists to gather more information on the issue.

They are also asking the public to go to local museums and galleries and count how many works are by men and by women and post them on social media as part of the campaign to highlight the representation of female artists.

A recent report said that only 4% of the National Gallery of Scotland's collections are by female artists, and 35% of the Tate Modern's collections.

The Artfinder report says only one of the top 100 lots sold at auction in 2015 was by a woman, and none of the top ten richest living artists are women.

It points out that the gap in value for the highest value items by male and female artists that year was $135 million (£108m) - $25 million (£20m) for Louise Bourgeois’ ‘Spider’, versus $160 million {£128m) for Picasso’s ‘Les Femmes d’Alger.

The report says the representation of women at large galleries such as MoMa in New York and the Tate was also too low.

Jonas Almgren, chief executive of Artfinder, said: "We’ve known for a long time that our [own] artists have pretty much a 50/50

gender balance, which is unusual in the art world.

"Women are still woefully underrepresented in the high-end art world and it’s remarkably overlooked as an issue.

"One of the biggest problems is a lack of reliable data, so that’s where we’re starting. As well as publishing our own data, we’re asking the world’s art institutions, museums and galleries to share their data. We know that will be a long and difficult road, but we’re taking the first step by publishing our data, and we hope that others will take on that mantle."

Artfinder works with 9000 artists and galleries.