LONDON — Its military reach has diminished. It has played little role in confronting Russia over Ukraine and strictly limited its response to crises in the Middle East and Africa. Its future in Europe is in question, and a recent snub of the Obama administration over China made clear that its alliance with the United States is no longer as central to either nation as it once was.

As Britain heads toward a general election on May 7, issues closer to home are at the top of the agenda. But the nation’s reduced involvement — and seeming loss of stature — on the global stage has become part of the political debate, echoing growing concern in foreign policy circles that Britain has ceded its longstanding reputation for “punching above its weight” and being Washington’s go-to ally.

“We’ve found ourselves not taking part in the biggest European crisis since the end of World War II; we’ve taken our distance under this government from Europe; and there has been a weakening of the trans-Atlantic component,” said a former senior British ambassador, asking to remain anonymous to avoid offending his current clients.

“Foreign policy has not been a priority, and both traditional pillars, Europe and the United States, are weaker,” the diplomat said. “And it’s difficult to say it won’t have some lasting effect, especially coupled with what is arguably our fastest disarming since the 1930s.”