Of 61 provinces and cities, the northern province of Hung Yen still has the highest average sex-ratio at birth of 131 boys for every 100 girls, Tien told the Nhan Dan (People) newspaper.
In the first five months of this year, the province's Nhu Quynh Town reported 38 female births out of 90 newborns.
Some of the province's communes such as Dinh Du, Chi Dao and Minh Hai had even more imbalanced ratios, with 257, 158 and 160 to every 100 girls, respectively.
Dr Pham Tuyet Mai, head of the Haiphong Municipal Obstetrics Hospital's delivery ward, said the ratio in the northern port city in the first three months increased to 116 boys for every 100 girls for the mother's first birth, 111.3 boys for every 100 girls for the second birth and 146 boys for every 100 girls for the third birth.
According to Vinh Phuc Province's report, its sex ratio at birth in the first four months of this year increased to 117.4 boys for every 100 girls. The report showed that the ratio was widening rapidly.
The ratio remains high for first and third births, especially among the high-income group.
Nguyen Thi Nga of Haiphong City's Centre for Population and Family said that most of families want to have sons in order to maintain the continuity of the family line and for security when they are old.
Luu Thi Hong, deputy head of Maternal and Child Health Department under the Ministry of Health, said that private health clinics are to blame for the continued gap as they provide counselling on how to have sons.
They also determine the gender of the foetus, which the law bans, and perform sex-selective abortions of female foetuses, she added.
Deputy Prime Minister Nguyen Thien Nhan has asked the Ministry of Health to give guidance on working programs to cities and provinces with the most imbalanced ratios.
Information will be given to the Party committees and the People's Committees of nine provinces, namely Hung Yen, Hai Duong, Bac Ninh, Bac Giang, Nam Dinh, Hoa Binh, Quang Ngai, Quang Ninh and Vinh Phuc, and the city of Haiphong.
Under these programs, the ministry will try to control sex selection of foetuses.
Nhan has also asked the Ministry of Education and Training to provide education on gender inequality and reproductive health at high schools as well as to raise awareness among the public.
Clinics that perform foetal gender diagnosis and sex-selective abortion should be punished and cease their operations.
In January, the Ministry of Health signed an agreement with the Vietnam Fatherland Front, Vietnam Women Union's Central Committee and relevant authorities to conduct public education campaigns on issues of population and reproductive health.
It has also provided the Ministry of Education and Training with updated information on population figures and reproductive health.