David Miliband, the Foreign Secretary, has taken an unspecified period of paternity leave after announcing that he and his wife have adopted a second child.

Mr Miliband and his wife, Louise Shackelton, who is American, flew back to Britain yesterday after adopting a newborn boy in the United States. They have named him Jacob.

The couple’s announcement coincided with Mr Miliband’s failure to arrive at a conference on British-Saudi relations in London. He was scheduled to attend with his Saudi counterpart, Prince Saud al-Faisal, but sent Kim Howells, a Foreign Office Minister, in his place.

The abrupt nature of the statement reflects a sensitivity on the part of the Milibands who, friends say, were deeply hurt by the media reaction after they adopted their first son, Isaac, in December 2004, also in the US.

The couple said that they were “delighted by the new arrival” and asked the media to protect their privacy.

They decided to delay their announcement until the last possible moment to avoid British reporters trying to find them while they were still in the United States, and so possibly identifying the birth mother.

The US adoption system is far more liberal than the highly restrictive regime that operates in Britain, which makes it virtually impossible to adopt a newborn baby. Private agencies, charities and religious groups match couples with babies in the US, unlike in Britain, where only local authorities act as intermediaries.

About 4,000 children are adopted each year in Britain, and only a fraction are aged 1 year or under. In the US, about 30,000 babies are adopted every year.

The biggest difference is that in the US parents are frequently matched with babies before the birth. Prospective parents often meet the natural mothers when they are pregnant and can even be present at the birth. The Milibands were at the birth of their first child in 2004.

They also pay her medical expenses, which can reach $50,000 (£24,000).

In Britain, everything possible is done to try to persuade a natural mother to care for her baby. If she will not or cannot, babies and children are placed in the care system before adoption can take place. There is a lengthy process to approve babies for adoption which means that most children are usually more than a year old when they go home with their new parents.

A spokesman for the Foreign and Commonwealth Office declined to say whether Mr Miliband was present for the birth this time, but sources told The Times yesterday that Jacob was born about two weeks earlier than expected.

“There are very good reasons to do with the child’s rights to discover in his own time details about his birth and that is why we are not giving out any more detail,” the spokesman said.

Government sources said that the Saudis were told when the baby was born that there was a possibility that Mr Miliband would be unable to attend the conference in London, although they were not told why.

The Foreign Secretary still hoped he might be able to return in time, but there were delays in completing the adoption procedures after the baby’s birth and in arranging a visa, and Mr Miliband decided to return with his family rather than fly back to London alone to keep his engagements.

“Everyone – the Queen, the Saudis, the Prime Minister – was completely signed up,” a source close to Mr Miliband said. “He didn’t want to have a situation where the press were camped outside a hospital.”

In a sign of his anxiety not to risk giving any offence during the state visit by King Abdullah, Mr Miliband arranged to break his period of leave for a meeting with Mr al-Faisal, which will probably take place today.

When Mr Miliband announced the adoption of his first child three years ago, he and his wife revealed more details, including the date of his birth and his weight, and confirmed that were present at the birth.

They were upset by the controversy that followed, as the Conservatives asked whether Mr Miliband, then a minister at the Education Department, had benefited from having his application for adoption fast-tracked.

Adoption rules

IN BRITAIN
— Local authorities are in charge of adoption
— Babies and children are adopted from the care system, not at the time of birth
— Legal process that determines which babies and children are “eligible for adoption” is lengthy and often challenged in court by the natural parents. So only a few hundred babies under the age of 1 are adopted each year

IN THE UNITED STATES
— Private agencies church and voluntary groups match parents with babies
— Natural mothers have a say in who can adopt their child and can ask to meet the prospective parents
— The natural mother usually has medical bills paid by the adoptive parents, who sometimes attend the birth

Times Recommends

• Sarah Brown says 'no thanks' to veal at G8 - twice
• Stockton-on-Tees is obesity capital of Britain
• Stores blame poor sales on Murray factor