New Zealand has kept its top spot as the country perceived to have the least corruption, an honour it shares with Singapore and Denmark.

Last year it held the top spot on its own but now shares the kudos of being perceived to have the lowest level of public sector corruption out of 178 countries, according to global corruption campaigner Transparency International's 2010 Corruption Perceptions Index (CPI).

New Zealand has a composite score of 9.3 out of 10, slightly lower than the 9.4 score it had last year.

At the other end of the scale, Somalia occupies bottom spot with a composite score of 1.1 while Myanmar (1.4), Afghanistan (1.4) and Iraq (1.5) dwell in the other bottom placings.

Alex Tan, Transparency International NZ director, says New Zealand's result is pleasing but warned of getting too complacent about the results.

''The CPI measures perception of corruption and not hard data. We note that in April this year the Serious Fraud Office announced an investigation into serious allegations of corruption at a public entity [ACC],'' Tan says.

''The CPI only measures the degree to which corruption is perceived to exist among public officials and politicians in New Zealand. It does not take into account the attitudes of the private sector when conducting business here and overseas.''

He's concerned about the apparent lack of awareness about corruption amongst New Zealand's private sector.

The government, he says, must do more to strengthen the regulatory and legislative environment in respect of combating bribery and corruption. Although New Zealand signed the United Nations Convention Against Corruption (UNCAC) in 2003, it is one of only 18 countries not to have ratified it. He says 122 countries have both signed and ratified UNCAC.

"For a country that consistently tops the CPI, the fact that seven years after signing UNCAC we still have not ratified it is somewhat hard to fathom.''