This press release (boldface mine):

The ICRC is profoundly concerned over any practice that humiliates and degrades detainees; its work in places of detention in Iraq and around the world aims precisely at preventing abuses that violate international law.

ICRC delegates regularly visit Abu Ghraib and other places of detention in Iraq (including those under the responsibility of UK forces). At Abu Ghraib visits have taken place about every 5-6 weeks since late last year when the US began to intern Iraqis and other nationals at the prison.

In Iraq, as elsewhere, ICRC delegates speak with the detainees in private to monitor their treatment. Following its visits, the ICRC conveys its findings and recommendations to the detaining authorities by making an immediate report to the authorities on the spot and then presenting its findings and recommendations in writing to their superiors.

In these reports – which are confidential so as to prevent humanitarian issues from becoming politicized – the ICRC requests that appropriate action be taken, where necessary, to stop the mistreatment of prisoners or to improve their conditions.

In the specific case of Abu Ghraib, the ICRC has - to the best of its knowledge - been granted unimpeded access to all detainees and all sections of the prison since last year. The ICRC, aware of the situation in Abu Ghraib, and on the basis of its findings, has repeatedly requested the US authorities to take corrective action.

Along with other legal norms, international humanitarian law prohibits torture and mistreatment at any time, irrespective of the status of the person detained. Reports of such acts must be properly investigated and perpetrators brought to justice. Detaining authorities are also duty bound to take all necessary measures to prevent any such abuses happening or recurring.

If their visits have been impeded, they aren't mentioning it. Note the pointed remark about politicizing humanitarian issues. The Red Cross report circulating around was not supposed to have been released to the public.