The Vanuatu Daily Post reports Napat met with the British High Commissioner Nicolette Brent in Port Vila "to seek justifiable explanation on the decision".
Napat said the Vanuatu government had been actively working to bring in the necessary reforms to its citizenship program to meet requirements set by the European Union.
The UK is no longer in the EU. However, the EU Council last year also decided to remove Vanuatu's visa-free-access to EU countries, a decision that came into effect on February 4 this year.
"During the meeting, Napat expressed his profound dissatisfaction with the decision of the British government," the Daily Post reported.
"The decision to end the visa exemption to Vanuatu citizens will have great impact on Vanuatu's economic development and does not reflect the true spirit of friendship and partnership that binds the two countries together, prompting the Minister to question the UK's commitment to Vanuatu's development agenda," it added.
Foreign Minister Napat also expressed his concerns over having no opportunities for negotiation and dialogue between the two governments.
However, the UK Home Department secretary of state Suella Braverman said the decision to impose the visa requirement was not a sign of poor relations between the countries.
Braverman said careful consideration of Vanuatu's operation of a citizenship-by-investment scheme has shown clear and evident abuse of the scheme, including the granting of citizenship to individuals known to pose a risk to the UK.
She said the decision to impose these visa requirements has been taken solely for migration and border security reasons, and it is not a sign of poor relations with these five countries.
The changes to the immigration rules came into effect from July 19 and there will be a grace period for those who already have travel bookings, made on or before the changes came into force, as long as they arrive no later than August 16.
The Vanuatu government will thoroughly examine the implications of the decision and formulate a comprehensive response.
"The implications of the UK government's decision will meticulously analysed, and appropriate measures will be taken to address this national issue in a way that safeguards the best and long-term interests of Vanuatu's citizens who are still recovering from the devastating impacts of the two cyclones this year," the Daily Post reported.