The European Commission has said that member states will be given time to enforce new vehicle emissions limits, out of recognition that some are struggling to meet their targets.

Munich and Stuttgart admitted this week that they had already gone beyond the limits set, with other European cities expected to follow suit, Planet Ark reports.

EU Industry Commissioner Guenter Verheugen said that the emissions rules would not be rigidly enforced just yet.

"The Commission won't start swinging the big stick and talking about treaty breaches straight away. We'll look at the experience of the first year and then we'll have to decide," he said.

The soft approach has met with criticism from environmental groups, including lobby group BUND.

"Clean air in cities and liveable communities are more important. If necessary, road traffic has to take a secondary place to this," BUND director Gerhard Timm argued.

However Mr Verheugen denied that he was lax on emissions, pointing out that he had already committed to further cuts to the limits on diesel particles, with proposals to reduce the limit to five milligrams of emissions per kilometre soon to be unveiled.

Measures to cut transport emissions are currently being implemented in cities across Europe, including increases on taxes on petrol and diesel to pay for green buses and partial traffic bans, with tax breaks for diesel engine filters under consideration.