President Bush sidestepped the Senate and installed John Bolton as US Ambassador to the United Nations today.

The President invoked a rarely-used executive power to fill important posts while the Senate is in recess to end a five-month impasse with Democrats, who refused to accept Mr Bolton's nomination.

During Mr Bolton's protracted confirmation hearings, Democrats accused Mr Bolton - currently the Undersecretary of State for arms control and international security - of bullying subordinates and twisting intelligence to fit his conservative ideology.

The appointment of Mr Bolton, a plain-spoken hawk who has been a fierce critic of the UN in the past, was confirmed at a ceremony at the White House this morning.

"This post is too important to leave vacant any longer, especially during a war and a vital debate about UN reform. So today I’ve used my constitutional authority to appoint John Bolton as America’s ambassador to the United Nations," said Mr Bush.

"The United States Senate held thorough confirmation hearings and a majority of United States senators agree that he is the right man for the job. Yet, because of partisan delaying tactics by a handful of senators, John was unfairly denied the up-or-down vote that he deserves.

"I’m sending Ambassador Bolton to New York with my complete confidence."

Mr Bolton said he would work tirelessly in his new job and said it would be "a distinct privilege to be an advocate for America’s values and interests at the UN, and, in the words of the UN charter, to help maintain international peace and security".

The move to appoint Mr Bolton, 56, over the heads of the Senate in what is known as a "recess appointment" was widely expected in Washington over the weekend. But Mr Bush's exercise of the rarely-used power just three days after the Senate closed for the summer attracted immediate criticism today.

"It’s a devious manoeuvre that evades the constitutional requirement of Senate consent and only further darkens the cloud over Mr. Bolton’s credibility at the UN," said Senator Edward Kennedy of Massachusetts, on hearing of the appointment.

Until this morning, Mr Bolton's nomination had been caught in an apparently intractable confirmation process. His name was put forward by the White House in March, but in May, the Senate Foreign Relations Committee refused to endorse his candidature and Democrats then threatened to block his nomination should it reach the Senate floor.

Democrats have accused Mr Bolton, who has a distinctive moustache, of intimidating his staff and misusing US intelligence, as well as showing a marked disdain for the UN as an institution of international government.

As recently as Friday, 35 Democrat Senators and one independent sent President Bush a letter urging him to find a different UN envoy. Their letter followed an earlier petition signed by 102 current and former US ambassadors protesting at his candidature.

Yesterday, as rumours circulated of President Bush's intention to use the summer holiday to appoint Mr Bolton without Senate approval, Senator Christopher Dodd of Connecticut, a senior Democrat on the Senate Foreign Relations Committee said that such a move would be proof that Mr Bolton was "damaged goods".

"He’s damaged goods. This is a person who lacks credibility," Senator Dodd told the Fox News television channel.

"This would be the first UN Ambassador since 1948 we’ve ever sent there under a recess appointment. That’s not what you want to send up, a person that doesn’t have the confidence of the Congress," Senator Dodd added.

But Mr Bolton has admirers as well as critics. Conservative supporters cite his abrasive and uncomplicated style - he once joked that "If the UN secretary building in New York lost 10 stories, it wouldn't make a bit of difference" - and say that he is the right choice to shake up the organisation, which they say is slow and ineffectual.

Although President Bush's appointment will take effect immediately, Mr Bolton will have to undergo the full Senate confirmation process when the the new Senate is convened after the mid-term Congressional elections in November 2006.

Times Recommends

• Rio Tinto four held as China prepares case
• Diplomats must keep heads down and trousers up
• When in Rome should one make like Berlusconi?