British diplomats said Tuesday that they will restate to the State Department their concerns about the U.S. military’s treatment of Pfc. Bradley E. Manning, the soldier who is accused of supplying confidential diplomatic files to the WikiLeaks Web site.

Britain’s Foreign Office said that after a late-night debate in the House of Commons on Monday, it would instruct officials at the British Embassy in Washington to reiterate their concerns.

Manning, 23, has been detained in the brig at Quantico Marine Corps Base since his arrest in May. He is held in solitary confinement for 23 hours a day and is forced to surrender his clothing each night and wear a “smock” to bed.

Manning’s attorney has written on his blog that Manning, despite having a Welsh mother, does not hold a British passport or consider himself British.

“It is clear that he neither is asking for our help, nor considering himself to be British,” the Foreign Office minister, Henry Bellingham, said in Monday’s parliamentary debate. Still, he noted, under British law, Manning is “British by descent.”

Bellingham said British officials first raised their concerns with the State Department on March 29 and would “instruct our officials at our embassy in Washington again to report the concerns of this House to officials in the State Department.”

He noted that President Obama had reported receiving assurances that Manning’s treatment is “appropriate” and meets “basic standards,” but he emphasized that conditions “must meet international standards.”

Ann Clwyd, the Labor lawmaker who raised the issue in Parliament, said in an interview that Manning’s treatment “is appalling, and you know, unless we complain about it, we’re acquiescing.”