Sonny Bill Williams taped over the Bank of New Zealand logos on his Blues jersey for their match against the Highlanders on Saturday.

It has since emerged that Williams, who is a Muslim, was taking a religious stand on the issue of banks charging interest and fees on loans.

'Sonny Bill Williams has lodged a conscientious objection with New Zealand Rugby in his contract to finance companies, banks, alcohol companies, tobacco companies and gambling companies,' NZ Rugby confirmed in a statement.

BNZ said it didn't have a problem with Williams' stance.

'He's entitled to have religious beliefs and customs around that, and it's really between him and the Blues as to how that manifests itself. So we have no issue with it.'

However, that didn't stop New Zealand's prime minister Bill English from questioning Willliams' actions.

'It is hard to understand that one guy has to behave differently than the rest,' English told the AM Show on Monday. 'I don't understand all these professional contracts, but if you're in the team, you're in the team.'