The number of women who claim they were raped by British soldiers in Kenya over the past 20 years has doubled to more than 400, with lawyers investigating more than 200 new allegations this week. 

The fresh claims were made by women living in the area around the remote Archers Post training ground in northern Kenya, who told lawyers they were raped by soldiers temporarily stationed in the area.

Altogether, more than 400 women have said they were attacked by soldiers in the British army in incidents stretching back to 1983. The Ministry of Defence has confirmed that the allegations are being investigated.

Among the new cases are more than 30 women from the Samburu tribe who allege they were raped by Gurkhas based at Archers Post in 1997. The elders of their community say that they made a complaint at the time to the district officer and to the commanding officer of the British army camp, who promised to investigate.

However, no action was taken, and the alleged rapes continued. One woman who has a mixed-race child under a year old claims that her pregnancy was a result of a rape in 2002. 

These fresh allegations add to a shocking toll. More than 200 women have already come forward from the Masai community around the town of Dol Dol in the northern highlands to allege attacks by British soldiers over the last 20 years. Many of these were gang rapes and at least six mixed-race children were born.

The British solicitor Martyn Day is planning legal action for compensation on behalf of the women. He told the Guardian: "I am totally convinced that the vast majority of women who have come forward are genuine. The evidence strongly points to British officers being aware of this and having done absolutely nothing." 

The Ministry of Defence originally said it had no record of any complaints being made to the army. But Mr Day and a Kenyan organisation, Impact, have uncovered evidence of complaints being made to army officers as far back as 1983. A team of military police is now in Kenya to investigate some of the allegations, the MoD said. 

The Guardian has spoken to several of the women whose claims are backed up by independent evidence, including medical and police records. One woman, Anna Tipita, said she was attacked by two soldiers in 1983. They raped, beat and kicked her in a brutal attack in which they broke her pelvis. She said: "Even if the British soldiers compensate me ... I will never be able to forget. They have brought shame on all the British people."