All replacement catalytic converters on cars and vans registered from March 2001 must by type approved from August 13.

The new law, which covers vans up to 3.5 tonnes and cars with up to eight seats, brings the UK up to the same standards as other major European markets.

All cats must be marked to show that they meet R103 and the Vehicle Certification Agency will do spot checks. People fitting units that don't meet the standard may face a fine of up £5,000.