British lawmakers accused the government of failing to show leadership over Ukraine on Friday in what the opposition Labour party said was "a growing chorus of concern" about Britain's foreign policy.
The report from a parliamentary committee said that Europe as a whole was guilty of "sleepwalking" into the crisis and Britain "has not been as active or as visible on this issue as it could have been".
The accusation resonates in Britain, where analysts said the last few years have seen a diminishing role for the second strongest NATO power and the third largest economy in the European Union.
The memory of the conflicts in Iraq and Afghanistan has made the public and the government particularly risk averse in foreign affairs, and budget cuts and electoral worries have played their part too.
"Britain's strategic ambition has shrivelled," The Economist weekly said, while columnist Nick Cohen wrote in The Guardian that "as far as a convulsed Europe is concerned, Britain might as well not exist".
More damaging were the words from General Richard Shirreff, until last March Britain's top commander in NATO, who said that on Ukraine, Cameron was "clearly a bit player".
"Nobody is taking any notice of him ... He is now a foreign policy irrelevance," he told The Times.
Ian Bond, director of foreign policy at the Centre for European Reform, a think tank in London, told AFP that there had been a "shrinking of ambition".
"We have become much more averse to getting involved," he said, adding that the current government was "obsessed with Europe as a negative".
In recent international diplomacy on Ukraine "it's been really extraordinary to see this diplomatic process led by France and Germany", he said.
The government has pointed out its strong position on sanctions on Russia over Ukraine, as well as its involvement in the campaign against the Islamic State group.
But that has left the critics unconvinced.
"David Cameron has been responsible for the biggest loss of British influence in Europe for a generation," said Douglas Alexander, the Labour party's spokesman on foreign affairs.
"As the crisis in Ukraine continues, it is vital that the EU maintain a united approach, and that the UK government play its part in helping find a diplomatic resolution to the conflict," he said.
Richard Whitman, an associate fellow at Chatham House think tank, also said there was a "lack of enthusiasm" and pinned the blame partly on the upcoming general election on May 7 in which Conservative leader Cameron is hoping to win a second term as premier.
"The Conservatives are very cautious. It's a very narrow general election if you read the opinion polls," he said.
Another reason for the tentative foreign policy, he said, was the impact of budget austerity on defence spending in Britain as well as "more deep-seated issues" of reticence after conflicts abroad.
Regular Russian bomber flights close to British airspace -- part of a pattern seen in different parts of Europe -- have helped fuel concern in Britain.
Following the latest incident this week, the former head of the British air force, Michael Graydon, complained to the Daily Mail newspaper about cuts.
"They fly in these regions to check our air defences and they have probably worked out we are not as sharp as we were," Graydon was quoted as saying.
"I very much doubt whether the UK could sustain a shooting war against Russia. We are at half the capabilities we had previously," he said.
Since 2010 when the current government came to power, the armed forces have been reduced by 18,000 personnel and the Royal Air Force now only has seven air fighter squadrons, compared to 33 in 1990.
"The cuts in defence spending reflect the loss of ambition," Bond said, adding that Britain could fall below the defence spending target for NATO members of two percent of gross domestic product (GDP).
On NATO, however, The Economist said that Britain was "pulling its weight" in efforts to reassure eastern European states by playing a leading role in the alliance's new 5,000-strong rapid deployment force.
Cameron on Friday unveiled an £859 million (1.2 billion euro, $1.3 billion) contract for BAE Systems to build new warships for the British navy.
"This is a substantial investment in our shipbuilding industry," the premier said, underlining that it was part of the government's economic plan to invest £160 billion in defence equipment over the next 10 years.