More than half of drivers involved in crashes where someone was killed or injured were not tested for their alcohol level in the second half of last year, new figures have shown.

This is despite mandatory breath testing being introduced last year for those at the scene of all road crashes where someone has been killed or injured.

320 drivers were involved in such crashes between July and December 2011, but according to garda figures, 175 of them could not be tested.

107 drivers were involved in fatal crashes in that time and of those, 62 were not tested. Of 213 involved in a serious injury collision, 113 could not be tested.

The figures emerged from the Department of Justice in response to a parliamentary question from Deputy Tommy Broughan.

Reasons for not testing included that the driver was removed to hospital, fatally injured or was unknown. In crashes involving a serious injury they also included accidents when there was insufficient time to conduct the test, or where the driver was arrested.

In 8% of crashes the driver was not tested because a garda formed an opinion alcohol was not a contributory factor to the cause of the crash.

In two such cases someone was killed, while in 24 a serious injury was incurred.

PARC, a group representing victims of road accidents, says members are shocked and angry that testing was not being carried out despite the change in the law.

Minister for Transport Leo Varadkar said that under the law as it stands anyone who is involved in a collision causing a serious injury has to be mandatorily breath tested.

He noted that there are exceptions within the law where it would damage the person's health to have a breath test, where someone has died, or where they have been arrested anyway.

But he said he is concerned that the law perhaps is not being enforced fully.

And he said that that is something he is going to have to discuss with the Garda Commissioner and the Minister for Justice.

He said that it is important that laws enacted by the Oireachtas are enforced.

The Garda Press Office said it would be inappropriate to comment on correspondence between members of the Oireachtas but pointed out that there were a number of exemptions to mandatory testing, such as in cases where it might damage the person’s health.

The Irish Medical Organisation and PARC have called for monthly reports to be made available to show how many drivers are being tested - and explanations where necessary as to why they are not.

The IMO also said that the figures were an improvement on the situation previous to the legislation being implemented, when only one in 10 people involved in crashes were being tested.