EU probe call
Transport Secretary Patrick McLoughlin said: "We are closely monitoring the situation and have been pushing for action at a European level for more accurate tests that reflect driving on the road.
"It's vital that the public has confidence in vehicle emissions tests and I am calling for the European Commission to investigate this issue as a matter of urgency."
Meanwhile, German Chancellor Angela Merkel called for "full transparency" from VW in clearing up the case.
"The [German] transport minister is in close contact with the company, VW, and I hope the facts will come to light as soon as possible," she told reporters.
Earlier, French Finance Minister Michel Sapin also called for an EU inquiry, but a UK car industry spokesman said there was "no evidence" of cheating.