The paper reported that, for the first time, female soldiers were accused of aiding in the sexual and physical abuse of detainees.
Armed forces minister Bill Rammell said in a statement that the claims were being taken seriously, but that formal investigations needed to take place “without judgements being made prematurely”.
He told the BBC that not all the cases were new and “that about seven have come in within the last month”.
In one case, soldiers are accused of piling Iraqi prisoners on top of each other and subjecting them to electric shocks, the Independent reported.
The paper compared it to the abuse at the notorious US detention centre at Baghdad’s Abu Ghraib prison.
One abuse claim relates to a 16-year-old boy who says he was raped by two British soldiers while he was in custody in 2003. Others say they were stripped naked, abused and photographed.
A public inquiry is already under way into the death of an Iraqi civilian, Baha Mousa, who died in British custody in Basra in 2003 after sustaining 93 separate injuries to his body.
Shiner, who is representing Mousa’s family, told the BBC he believed “there are hundreds of cases that are going uninvestigated”.
But the Ministry of Defence (MoD) said instances of abuse were isolated cases.
“There is not any endemic evidence of abuse within the armed forces, and that is in the context of 120 000 (troops), the vast, vast, majority adhering to the highest standards of behaviour,” defence minister Rammell told BBC television.
Shiner, conceded that claims still needed to be tested against fact, but called for a public inquiry into all of them.
“It is very important now that there should be no further attempt by this government and the MoD to sweep this under the carpet the ‘few bad apples’ thesis does not work,” he told the BBC.
Tom Porteous, director of Human Rights Watch, which has a track record of investigating abuse by US forces in Iraq, said he was aware of the 33 cases mentioned.
“These are cases that involve many more soldiers, obviously, and because of the seriousness and the credibility of the allegations, we are conducting our own inquiry and will produce our own report,” he told BBC television.
Britain has withdrawn almost all of its troops from Iraq. Only 100 naval trainers who are helping to protect Iraq’s southern oil terminals remain. They are expected to stay for another year.