The former human rights lawyer Phil Shiner has pleaded guilty to fraud charges linked to claims made against Iraq war veterans.

Shiner, 67, appeared at Southwark crown court on Monday and pleaded guilty to three counts of fraud, according to the National Crime Agency (NCA). He will be sentenced on 2 December.

Shiner, from Birmingham, was the principal solicitor of the law firm Public Interest Lawyers. He made an application to the Legal Services Commission in 2007 in which he sought up to £200,000 of legal aid funding for his firm to represent clients including Khuder Al-Sweady, in an application for judicial review.

According to the NCA, Shiner received about £3m in the value of the contract, and the ensuing Al-Sweady inquiry cost the UK taxpayer £24m.

In making his application, Shiner failed to disclose that an agent acting on his behalf and with his knowledge had been cold-calling and making unsolicited approaches to potential clients in Iraq. He also failed to disclose that he was paying referral fees.

This practice was not permitted as part of gaining a legal aid contract, the NCA said.

He was also convicted for providing a witness statement to the commission in support of his application, which was again gained via an unsolicited approach.

As a result of his failure to disclose this information, Shiner was able to gain a “valuable legal aid contract to enable him to pursue the judicial review”, the NCA said.

Andy Kelly, the head of the NCA’s international corruption unit, said: “This conviction is a milestone in what has been a thorough and complex domestic and international investigation. Shiner’s actions resulted in untold pressure and anxiety on members of the British armed forces, pursuing legal challenges funded through dishonest actions.”