The Singapore Tourism Board (STB) said yesterday it had suspended travel agency TG Tours for two months until July 14.
During this period, TG Tours will have to fulfil existing obligations to customers, but cannot accept new bookings.
It comes in the light of a tour conducted by an unlicensed tourist guide working for TG Tours in October 2014, which breached requirements under the Travel Agents Regulations.
Those who provide paid guiding services must hold a valid licence, unless specifically exempted.
The guide was in the midst of giving a tour when an STB enforcement officer checked his credentials and discovered he did not have a licence, said the director of travel agents and tourist guides at STB, Ms Ong Ling Lee.
TG Tours was prosecuted for using an unlicensed guide, which earned it a warning.
But the guide himself left Singapore before enforcement action could be taken.
STB has obtained a warrant of arrest for the Vietnamese national.
This is the fourth case of a travel agent having its licence suspended by STB since the start of the year, and the first this year for using an unlicensed tour guide.