Downing Street has insisted David Cameron followed all the "proper processes" after it emerged his Nepalese nanny has been granted British citizenship.
A spokeswoman said neither the Prime Minister nor his wife Samantha wrote letters in support of Gita Lima's application and that "t he normal application process was followed throughout".
"As is usual, Mrs Cameron was named on her application as her employer," Number 10 said of the successful bid which was granted in late 2010.
Questions were raised about Mr Cameron's use of foreign domestic help after a minister deplored the effects of the "metropolitan elite" using cheap migrant workers.
Home Office minister James Brokenshire said the wealthy had been the main winners from Britain's openness to labour from abroad, because they had to pay less for tradesmen and services.
The losers had been ordinary workers whose wages had stagnated, he added.
"The immigration system we inherited was not designed to benefit this country or the people who live here," the Tory minister said in a speech to the Demos think-tank yesterday.
"For too long, the benefits of immigration went to employers who wanted an easy supply of cheap labour, or to the wealthy metropolitan elite who wanted cheap tradesmen and services, but not to the ordinary, hard-working people of this country."
Mr Cameron has employed Ms Lima for several years since recruiting her through from Kalayaan, a charity that helps immigrants to escape abusive bosses.
She took a temporary leave of absence in 2012, during which an Australian nanny filled in.
No 10 initially stonewalled questions on whether it was appropriate for Mr Cameron to use foreign nannies, before disclosing that Ms Lima had been granted UK citizenship.
"The point is that the Prime Minister's nanny is someone who has come here, works hard and is now a British citizen," the spokeswoman said.
"I think you can expect that the Prime Minister would follow the normal process in the right way."
Asked whether Mr Cameron and his wife had chosen their nanny on the basis of cost, the spokeswoman said: "I think they were guided by someone who would look after their children in the way they wanted to."
Deputy Prime Minister Nick Clegg disclosed yesterday that he employs a Belgian national as a domestic help.
After Labour called for " complete transparency and openness" over whether there had been any contact between the Prime Minister and the Home Office on the case, No10 issues a further statement.
"Mr and Mrs Cameron's nanny became a British citizen in late 2010," ir said.
"Mr and Mrs Cameron did not write a letter supporting their nanny's application for British citizenship.
"The normal application process was followed throughout. As is usual, Mrs Cameron was named on her application as her employer."