The paintings have been acquired for Britain as it marks 100 years since women were allowed to vote

Four paintings by one of Britain's leading suffragettes, Sylvia Pankhurst, documenting the conditions of female workers in the early 20th century, have been acquired for the nation as it marks 100 years since women were allowed to vote.

The watercolours by Pankhurst, a key figure in the women's suffrage movement that was founded by her mother Emmeline, were painted during a tour of industries in 1907 to highlight the poor conditions and low wages faced by working-class women.

They have now been purchased from her family by the government-sponsored Tate gallery network.

"At a time when gender pay gaps and women's rights at work remain urgent topical issues, these images remind us of the role art can play in inspiring social change," Ann Gallagher, director of collections for British art, said in a statement.

Pankhurst, who died aged 78 in 1960, was among the leading figures in militant organisations in the early 20th century pushing for women's rights and votes.

It was not until 1918 that Britain granted women aged over 30 who met a property qualification the right to vote and to run for parliament. They had been able to contest local elections since 1907.

Pankhurst used her art as a campaigning tool, and created the four paintings during a trip to research and document the lives of poor working women in northern England and Scotland.

Two of the watercolours show cotton mills in Glasgow, Scotland, where Pankhurst later described "the almost deafening noise of the machinery and the oppressive heat", saying she was "so hot and airless that I fainted within an hour".

The other two show Staffordshire potteries, in northern England, where women were often restricted to lower-paid jobs and exposed to flint dust and fumes from lead glaze.

The pictures were purchased from her grandchildren, Helen and Alula Pankhurst, and will go on display at the Tate Britain in central London in 2020, the gallery said.

"Sylvia was an artist as well as a champion of working women's rights, her first passion not as well known as her second," Helen Pankhurst, who is also a women's rights campaigner, said in a statement.

"In these beautiful pieces these interests are powerfully combined."