Singapore has taken fourth spot in an annual ranking of countries deemed to have the least corruption in the public sector, tying with Switzerland and Sweden in its scoring for the second year running.

The three countries maintained their score of 85 on graft watchdog Transparency, which ranks countries on a scale from zero, for highly corrupt, to 100, for very clean.

Singapore remains the only Asian country placed in the top 10.

Denmark and New Zealand - consistent front runners for years - tied for the top spot with 87 points on the index, released on Thursday (Jan 23).

Finland, which had tied previously with Singapore, Sweden and Switzerland for third place in the 2018 index, pulled ahead of the pack by one point. It now ranks third at 86 points.

The report by Berlin-based Transparency International noted that a "staggering" number of countries showed little to no improvement in tackling corruption, despite anti-graft movements gaining momentum globally.

Two-thirds of the 180 countries scored below 50, with an average score of only 43, similar to 2018.

Since 2012, only 22 countries, including Greece, Guyana and Estonia, have significantly increased their scores, while the scores of 21 countries declined considerably.

Canada, a consistently top performer, dropped four points from the previous year to 77. Transparency International highlighted the conviction of a former executive of construction company SNC-Lavalin in December last year over bribes the company paid in Libya, a case linked to Prime Minister Justin Trudeau.

The United States earned 69 points, its lowest score in eight years. Transparency International noted that Americans' trust in government is at a historic low of 17 percent, according to the Pew Research Centre.

It also highlighted factors such as threats to the US system of checks and balances and an increasing influence of special interests in government that has affected its 2019 score.

The Corruption Perceptions Index started in 1995, ranks 180 countries and territories by their perceived levels of public sector corruption, according to experts and business people. It draws on 13 surveys and expert assessments to derive a score for each country.

In the 2019 index, Norway was in seventh place with a score of 84, followed by the Netherlands (82), Germany (80) and Luxembourg (80).

Corrupt Practices Investigation Bureau (CPIB) director Denis Tang said in a statement: "While Singapore has done relatively well in the fight against corruption, as attested to by several international surveys, we must not allow this to lull us into a sense of complacency.

"In fact, we must work even harder to ensure that incorruptibility remains part of the DNA of every Singaporean."

CPIB noted Singapore's good standing in other global indicators such as the Political and Economic Risk Consultancy's 2019 Report on Corruption in Asia, which has ranked Singapore the least corrupt country in the region since 1995.

Lawyer Wilson Ang said of the index: "Even though we have slipped a place from third to fourth, this is not a significant decline.

Mr Ang, who heads Asia regulatory compliance and investigations practice in global law firm Norton Rose Fulbright, added: "What is more important is that Singapore should continue to keep pace with global developments and update our laws to address the corruption risks in doing business."

He noted that some regional countries which ranked lower on the index - Malaysia, India and Thailand, for instance - have recently updated their laws on corporate liability and compliance practices to bring them more in line with mature jurisdictions such as the US and United Kingdom. This will make it easier to prove corruption at a company level, not just an individual one.

"I think Singapore ought to review our laws and implement a more consistent and workable test for corporate criminal liability and also to give credit and a legal defence to companies which have, in good faith, implemented anti-corruption compliance programmes," he said.