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Safety legislation in Europe requires car seats to pass a crash test at 30mph.

The Consumers' Association and AA Motoring trust want the test speed increased to 40 mph and made more realistic to take a side impact into account.

Ninteen seats commonly available in the UK were put to the 40mph test - and four of those performed badly.

Advice to parents from the AA motoring trust

Make sure that any seat will properly fit into the specific model of car Make sure you take time to fit it even if you're in a hurry Keep children in seats with harnesses for as long as possible

The Chicco Zenith, Meggy Combi, and the Mothercare Dimension and Runner were criticised for their performance in front on crashes and their overall safety and ease of use.

Chicco claimed the seats sold in the UK do not have the same harness as the one the researchers found fault with.

Mothercare was initially unable to comment on the criticism of its seats.

But Meggy said its Combi seat "exceeds the most recent and stringent legal requirement for automotive child restraint systems."

Another four seats available in the UK only gave the bare minimum protection - they were three models made by Britax and one by Mamas and Papas.

"The car seat industry has a long way to go," said Helen Parker, editor of Which?

"We're working together with consumer groups across Europe and car clubs such as the AA to guide people towards the safest seats."

Andrew Howard, head of road safety at the AA Motoring Trust, said: "These tests were carried out in laboratories with the seats fitted exactly as the instructions demanded, but despite this the results were often poor, and sometimes alarming.

"But there's no doubt that in real life things would be even worse, as many of the seats proved difficult to fit."

Car test results

These are the results of tests carried out at 40 miles per hour by the AA Foundation. All the car seats listed meet current safety standards, but some performed badly in the tougher 40mph test:

Rear facing baby seats to one year:
Satisfactory Bebe Confort Elios Safe Side, Brevi Smart Silverline, Britax Rock a Tot Deluxe, Graco Autobaby with base, Mamas and Papas Primo Viaggio (no seats in this category rated poor)

Forward-facing seats: 1-4 years
Good Romer Duo Plus
Satisfactory Britax Eclipse, Britax Renaissance, Maxi Cosi Priori SPS, Maxi Cosi Priori XP
Poor Chicco Zenith

Two Way seats: 0-4 years
Satisfactory Bebe Confort Iseos Safe Side

Booster seats: children up to 12
Good Britax Kids.
Satisfactory Bebe Confort Hipsos Safe Side
Bare Minimum Britax Cruiser Plus, Britax Ranger, Britax Trio, Mamas and Papas Pasaggio.
Poor Meggy Combi, Mothercare Runner, Mothercare Dimension