The IRFU and GAA stadium director Peter McKenna yesterday reiterated that the mixed synthetic and real grass surface at Croke Park is not a safety concern for rugby players despite some scathing comments from GAA players during last summer's championship season.

While none of the Irish rugby players have yet taken part in a training or practice session on the surface and are therefore not in a position to make a considered judgment, the IRFU have said their staff are working alongside staff at Croke Park to ensure the surface will be suitable for the two Six Nations Championship matches.

"The IRFU ground staff will be working closely with the Croke Park ground staff in an advisory capacity only," said an IRFU official. "No, we do not have any concerns over the safety of our players playing on the Croke Park surface."

The new pitch, which is also similar to the London Irish Madejski Stadium, was laid during spring-summer 2002 and has synthetic fibres running through it. During installation computer-controlled machines injected a special yarn into the ground to a depth of approximately 20cm, leaving 2cm above the surface.

A rye grass especially developed for Croke Park was then seeded between the artificial grass fibres. It is a natural, hard-wearing grass and has a quick recovery time, taking between only four and six weeks to grow. The close proximity of the stitching and the natural grass roots growing around the stitching is what gives the pitch its stability.

The system is employed in a number of English soccer stadiums, including Anfield, Upton Park and Villa Park. The pitch is also cambered, being 30cm higher at its centre than at the edge to assist drainage.

However, in July during the championship match between Clare and Wexford, Clare manager Anthony Daly was acutely concerned with pitch conditions, while Colin Lynch was taken off with an ankle injury that was blamed on the pitch. Other Clare players complained of rock-hard surface. "The number of guys who are slipping . . . and we tried every possible stud. Every guy changed his boots at half-time and still you had fellas slipping," said Daly. "It's lovely to stand on but when you try to run and turn it's dangerous . . . it's like concrete underneath. Colin Lynch wasn't anyone's fault but the field."

At the time the hard conditions were explained by the unusually fine weather as well as pitch invasions from Dublin fans and a series of concerts in the stadium, which were all said to have contributed towards compressing the ground.

"It's very slippery," said Cork's Joe Deane after the All-Ireland hurling semi-final in August. "There just seems to be something up with the surface. I know it was wet today but you could see with the football (played the previous day) as well that fellas were falling all over the place, no matter what boots they were wearing."

McKenna also defended the surface, although he admitted that they had done little to it other than aerate the soil since the championship with the intention of breaking up the ground and making it less hard.

"Eddie O'Sullivan has been to the ground and looked at the pitch and has not expressed any reservations about it," says McKenna.

"There are two ways of measuring hardness, objectively and subjectively. We measure it objectively, with hardness meters and we are well within the standards set by the sports governing body. They set the tolerance.

"The only issue is a heavy frost coming down on the day which would be an issue anywhere. The Desso surface tends to be harder than just grass but it is within those tolerance limits set by the sport."

The footballers and hurlers also complained about the bounce of the ball being higher than normal and also had problems over stud selection.

"Stud selection is for Eddie O'Sullivan and his players," said McKenna. "I don't see that as an issue at all. You have also got to look at other pitches which they have played on. Some pitches in New Zealand were extremely wet and the team also played in Russia some years ago in a qualifying event and that pitch was not up to international standards.

"The other thing to remember is that a rugby pitch is shorter than a GAA pitch, so the pitch will be pulled in from both ends that suffer from winter growth, especially the Canal end (southern end). While we have lights there, they are no substitute for sunlight but certainly they have helped us considerably with the growth."

Ireland's experience of playing on unsuitable pitches in the past is unlikely to help O'Sullivan and his team to beat France and England if some of the most gifted players in the game cannot keep their feet, and that Ireland play France in the second of their five games makes injury a particularly acute concern.

The Madejski Stadium cost more than £50 million to build and incorporates a system of synthetic fibres interwoven with natural grass. Rugby League action also took place on the surface with New Zealand thrashing the Cook Islands there in the autumn 2000.

"The surface is sometimes too good," said a London Irish official. "All the visiting teams love coming here because they can play rugby on it."