LONDON (Reuters) - Britain said it was concerned about its nationals imprisoned in Iran including a British-Iranian aid worker who has been detained since early April and accused by Revolutionary Guards of trying to overthrow Iran's government.

Nazanin Zaghari-Ratcliffe, who was arrested as she tried to leave Iran after a visit with her two-year-old daughter, appeared in the Revolutionary Court on Monday.

"We continue to raise our strong concerns about British prisoners in Iran, including Mrs Zaghari-Ratcliffe, at the highest levels in both London and Tehran," a spokeswoman for Britain's Foreign Office said.

Zaghari-Ratcliffe, 37, works for the Thomson Reuters Foundation, a London-based charity that is independent of Thomson Reuters and operates independently of Reuters News.

The Foreign Office spokeswoman said former Prime Minister David Cameron had repeatedly raised the case with his Iranian counterpart.

"We are deeply concerned by recent reports that Mrs Zaghari-Ratcliffe has been charged but has not been allowed to see a lawyer," the spokeswoman said.

"We remain ready to facilitate Mrs Zaghari-Ratcliffe’s daughter's return to the UK if requested."

(Writing by Guy Faulconbridge; Editing by Catherine Evans and Janet McBride)