The diaries of supporter Mary Blathwayt, kept from 1908 to 1913, show how complicated sexual liaisons - involving the Pankhurst family and others at the core of the militant organisation - created rivalries that threatened discord.

'Mary, who had been something of a favourite, often wrote quite bluntly about the situation. It does sound as if she was occasionally quite jealous,' said Professor Martin Pugh, an expert on the history of the movement, who came across the relevant and explicit pages in Blathwayt's little-known diary.

'This part of the diary puts the whole campaign in a truer perspective,' he added. 'All these women were under an enormous amount of pressure from around 1912, while the Home Secretary was trying to suppress their activities.'

Pugh, of Liverpool John Moores University, said the tensions felt, both physically and psychologically, meant the activists had to find sus taining relationships within their own ranks.

Emmeline Pankhurst and her three daughters, Sylvia, Christabel and Adela, were the leading figures in the battle to win votes for women. Founding the hardline Women's Social and Political Union in 1903, Mrs Pankhurst, as she was popularly known, went to prison 15 times for her political views and had a close relationship with the lesbian composer Ethel Smyth for many years following the death of her husband Richard in 1898.

'Dame Ethel had realised early on in life that she loved women not men and was fairly bold about things. They were often in Holloway together and shared a cell,' said Pugh.

Members of the union were social pariahs and the butt of music-hall jokes, but they were also criminals. Under the slogan 'Votes for Women and Chastity for Men', they bombed and set fire to churches and stations, threw bricks through windows, cut telegraph wires and tied themselves to railings.

'This was a period in which these women were carrying out something like guerrilla war - they felt they were engaging in battle with the Home Secretary, who was using all the tools of the state to oppress them,' said Pugh, who is researching a biography of the Pankhurst family.

Christabel was the most classically beautiful of the Pankhurst daughters and was the focus of a rash of 'crushes' across the movement. Pugh now believes she was briefly involved with Mary Blathwayt who, in her turn, was probably supplanted by Annie Kenney, a working-class activist from Oldham.

'Christabel was an object of desire for several suffragettes,' he said. 'She was a very striking woman.'

Many of the short-lived sexual couplings referred to in the diary took place in the Blathwayt family's Eagle House home in Batheaston, near Bath.

Kenney's frequent visits to Eagle House, and to the family's Bristol lodgings, receive most scrutiny from Mary Blathwayt. Pugh's research shows that her name can now be linked to up to 10 other suffragettes.

'Mary writes matter-of-fact lines such as, "Annie slept with someone else again last night," or "There was someone else in Annie's bed this morning," said Pugh. 'But it is all done with no moral opprobrium for the act itself.

'In the diary Kenney appears frequently and with different women. Almost day by day Mary says she is sleeping with someone else.'

Kenney, organiser for the South West, volunteered to join the suffragettes after hearing Christabel Pankhurst speak at a rally in 1905. The two were sent to prison together that year after disrupting a public meeting and had an intimate friendship for several years until Christabel became involved with another woman, Grace Roe.

While the affairs and one-night-stands at Eagle House provoked competitive rivalries, it is also clear they held the movement together. Many of the relationships provided emotional support for members of a group isolated from the rest of society.

'Biographers, while acknowledging a small lesbian element in the movement, have all skirted around the issue,' said Pugh.

'For those times the matter-of-fact tone Blathwayt adopts about the affairs did surprise me.'

The union suspended its militant activities to help the war effort in 1914 and women over 30 gained the vote in 1918. Equal suffrage was finally achieved in 1930.