Four men arrested under the Terrorism Act after a security alert at a hospital and later released without charge said yesterday they hoped lessons would be learned from their "traumatic experience".

The men, aged between 24 and 30, were kept in custody for two days after medical staff at Stafford General Hospital became concerned about their "suspicious behaviour" and the illness of a fifth man they were accompanying.

Their detention was criticised by Lord Carlile, the Government's independent reviewer of terror laws, who urged the Chief Constable of Staffordshire Police to apologise to the men and order an independent inquiry into his officers' use of the legislation.

In a statement released through the force, the four men said they had concerns about the way the investigation had been conducted and were considering their options.

The written document, issued on behalf of the men by the Independent Advisory Group, which was set up following their arrests, stated: "This has been a traumatic experience because of the intensive and intrusive nature of the investigation.

"We recognise that public security is a number one priority in modern policing. However, we do have some concerns with the investigative process to which we were subjected.

"We will discuss our concerns in private with the police in due course. Any further action will depend on this dialogue. Based on information received from hospital staff, and in the context of last week's royal visit, we feel that the police may have been acting in good faith.

"But it is hoped that lessons will be learned and that the correct balance can be achieved between protecting the public and respecting individual freedom."

Staffordshire Police said its investigation had found no links to terrorism and thanked the men for their "help and understanding".