Foreign secretary William Hague is playing an “avoidance game” over a gay US soldier accused of leaking classified documents to WikiLeaks, an MP has claimed.

Ann Clwyd, a Labour MP who is the former human rights envoy to Iraq, also accused the Foreign Office of “continued stonewalling” of Mr Manning’s mother, Susan, who is Welsh.

The 23-year-old American was held in solitary confinement until recently and concerns were raised about his treatment. He was required to strip regularly and was held in a bare cell.

Last month, he was moved to a medium-security prison in Kansas following lengthy assessments. He is now able to live alongside other prisoners and his surroundings have been described as more comfortable.

Mrs Manning wrote to the Foreign Office last month to ask officials to visit her son and check on his physical and mental health, the Guardian reports.

Ms Clwyd criticised the department for not responding to Mrs Manning’s letter within a week.

“Susan Manning also asked for any help that could be given, in Washington and elsewhere, to the family if they so request it,” she said. “At the very least, Mrs Manning, who is very concerned by the situation of her son, should have had the courtesy of a reply.”

She added: “This avoidance game they are playing can only be completely deliberate.”

Alistair Burt, parliamentary under secretary of state at the Foreign Office, said the department was “limited” in its actions because Mr Manning does not consider himself British.

However, Mrs Clwyd argued that Mr Manning is British by descent as his mother is Welsh.

Mrs Manning visited her son in February and said that conditions were having a “damaging” effect on him. She has also asked for consular assistant for future visits.

The Foreign Office said last month that the British embassy in Washington had relayed MPs’ concerns about Mr Manning’s treatment to the White House. it also confirmed that it was considered Mrs Manning’s letter and would reply shortly.