By Bryn Palmer

Wilkinson kicked seven out of nine goal attempts against Samoa

Jonny Wilkinson admits the new balls being used at the World Cup have left him feeling "helpless" on occasion.

The England star kicked seven from nine attempts at goal against Samoa but said the two missed attempts moved in the air despite there being no wind.

All Blacks fly-half Dan Carter also complained that he had not been allowed to practise with actual match balls.

"I don't care if I am kicking badly as long as I know it is me and I can work on it," Wilkinson told BBC Sport.

Interview: England fly-half Jonny Wilkinson

"The difficulty can be finding the accountability. You ask yourself, 'is it me or not?'. That is what affects my concentration.

"I missed a couple of kicks against Samoa and both were very heavy. They shifted quite a way, right to left, which is quite unusual for me, with no wind.

It is a bit like playing in a wind that you can't work out, it leaves you feeling a bit helpless Jonny Wilkinson

"The next kick, you are then asking yourself, 'do I allow for that, treat it as a one-off, or do I ignore it?'

"That is the tough part, you end up playing mental games outside a game, which you don't really want to be doing.

"It is a bit like playing in a wind that you can't work out, it leaves you feeling a bit helpless."

Ball manufacturers Gilbert said in a statement: "Gilbert will, of course, re-examine the balls sent back to them by the IRB [International Rugby Board] and will report should any inconsistencies be found."

Wilkinson is notoriously meticulous in his preparation for every facet of the game but particularly his goal-kicking, spending up two hours at a time practising.

606: DEBATE Give your thoughts on this story

He said it had be "an interesting few months" since the new balls were developed in the run-up to World Cup.

"People are trying to create balls that are perhaps easier for handling in the wet, or when you play night-time rugby and there is dew on the ball, but also on very dry days when your hands are very sweaty, which can be a lot worse," said Wilkinson.

"It has brought up issues with kicking the ball since the World Cup warm-up games, and it has given us a new challenge certainly.

Carter and other goal-kickers have struggled with the match ball

"I have been kicking better in practice than I did against Samoa, and after the game I just wanted to get straight back out there and thought: 'let's work on it again and find a way to beat it'."

Carter's concern, meanwhile, was that he had not been allowed to practise with actual match balls between matches.

The fly-half, whose career strike-rate is 80%, missed five place kicks out of nine in the All Blacks' 40-0 win over Scotland at Murrayfield despite the lack of wind.

"We've been using replica balls rather than being able to train with the balls we play with," said Carter.

But Gilbert denied teams were being forced to train with replicas.

Sometimes a brand new ball just doesn't fly as well Neil Jenkins

"All of the balls provided to teams for training prior to the tournament's commencement and to the RWC Organising Committee for the 48 matches are match balls. There are no 'replica' balls," the company said in a statement.

"All Gilbert match balls are 'pre-kicked' before dispatch to allow the stitch lines to settle and the ball to find its natural shape faster after inflation.

"Whilst taking very seriously the comments made by Dan Carter and members of the New Zealand management team following the game in Scotland last weekend, Gilbert remain supremely confident in the standard of balls delivered for use in the Rugby World Cup."

Welsh legend Neil Jenkins, the world record points scorer, is the principality's kicking coach, and he added: "For me, I just think these balls should be kicked in a lot earlier than they have been.

"It's important that you play with the ball you're going to use on a Saturday to get a feel for it, especially as a kicker.